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Plasma arginine vasotocin and angiotensin II concentrations during saline acclimation in birds with salt… Zenteno Savin, Tania 1991

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PLASMA ARGININE VASOTOCIN AND ANGIOTENSIN II CONCENTRATIONS DURING SALINE ACCLIMATION IN BIRDS WITH SALT GLANDS. By TANIA ZENTENO SAVIN B.Sc, Universidad Autonoma de Baja C a l i f o r n i a Sur La Paz, Baja C a l i f o r n i a Sur, Mexico A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER IN SCIENCES i n THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA Spring 1991 Tania Zenteno Savin In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Z o O c O C ^  The University of British Columbia Vancouver, Canada Date O-O^ usr y ^ t . DE-6 (2/88) A B S T R A C T Pekin ducks (Anas p l a t y r h y n c h o s ) , Canada geese (Branta  canadensis) and Glaucous-winged g u l l s (Larus glaucescens) responded d i f f e r e n t l y d u r i n g a c c l i m a t i o n t o s a l i n e e q u i v a l e n t t o f u l l s t r e n g t h sea water. A l l s p e c i e s were i n hydrosmotic balance u n t i l they were g i v e n 375 mM NaCl. When the b i r d s drank 75 mM NaCl ducks t r a n s i e n t l y decreased plasma sodium c o n c e n t r a t i o n ([Na +] p l) and o s m o l a l i t y (Osmpl) and i n c r e a s e d c l o a c a l Na + e x c r e t i o n ; geese t r a n s i e n t l y i n c r e a s e d h e m a t o c r i t (H c t ) , s u g g e s t i n g t r a n s i e n t e x t r a c e l l u l a r d e h y d r a t i o n ; and g u l l s i n c r e a s e d Osmpl (but not Hct) , s u g g e s t i n g t h a t t h e i r Osmpl had been below normal when f r e s h water was o f f e r e d . During a c c l i m a t i o n t o moderately c o n c e n t r a t e d s a l i n e , a l l s p e c i e s p r o g r e s s i v e l y i n c r e a s e d plasma a r g i n i n e v a s o t o c i n l e v e l s ([AVT] p l) (without concomitant i n c r e a s e i n Osmpl) and decreased plasma a n g i o t e n s i n I I c o n c e n t r a t i o n ([Ang H ] p l ) without p a r a l l e l changes i n Hct. F o l l o w i n g a c c l i m a t i o n t o 300 mM NaCl t o t a l body water (TBW) was i n c r e a s e d i n ducks and geese, but a c c l i m a t i o n t o 375 mM NaCl d i d not a f f e c t TBW i n g u l l s . When they drank 450 mM NaCl, ducks and geese decreased body mass and i n c r e a s e d Hct, plasma e l e c t r o l y t e and osmotic c o n c e n t r a t i o n s , [AVT] p l and [Ang I I ] p l , i n d i c a t i n g they were dehydrated. In c o n t r a s t , s a l i n e a c c l i m a t e d g u l l s d i d not i n c r e a s e [Ang H ] p l and i n c r e a s e d [AVT] p l l e s s than ducks o r geese. I n i t i a l [AVT] . was not s i g n i f i c a n t l y c o r r e l a t e d w i t h sex i n e i t h e r ducks o r geese. Female ducks i n c r e a s e d [Ang H ] p l and Osmpl l e s s than males d u r i n g exposure t o 450 mM NaCl, w h i l e female geese i n c r e a s e d [Ang I I ] p l more than males. S a l t g l a n d NaCl s e c r e t i o n and r e n a l water r e t e n t i o n c o u n t e r b a l a n c e d NaCl i n g e s t e d i n low t o moderately c o n c e n t r a t e d s a l i n e i n ducks, geese and g u l l s , but not i n ducks and geese d r i n k i n g s a l i n e e q u i v a l e n t t o sea water. G u l l s l i k e l y maintained simultaneous, c o n c e r t e d f u n c t i o n o f kidneys and s a l t glands d u r i n g h i g h s a l t i n t a k e , w h i l e c l o a c a l e x c r e t i o n may have decreased i n the Anat i d a e . Based on t h e i r r e l a t i v e s a l t s e c r e t i n g e f f i c i e n c i e s , plasma i o n i c c o n c e n t r a t i o n s , Osmpl and Hct i n c r e a s e d much more i n ducks than i n geese when they drank 450 mM NaCl, and remained unchanged i n g u l l s d r i n k i n g 375 mM NaCl. Release o f AVT and Ang I I i n b i r d s w i t h s a l t glands appears t o be c o n t r o l l e d by a c o m p l i c a t e d i n t e r r e l a t i o n s h i p between volume and t o n i c i t y ( t h r e s h o l d f o r r e l e a s e v a r i e s among s p e c i e s ) , and these (and p o s s i b l y other) hormones may a f f e c t s a l t g l a n d and kidney f u n c t i o n t o m a i n t a i n s a l t and water balance. i i i TABLE OF CONTENTS ABSTRACT i i LIST OF TABLES v i LIST OF FIGURES v i i i LIST OF ABBREVIATIONS i x ACKNOWLEDGEMENTS X INTRODUCTION 1 MATERIALS AND METHODS 6 EXPERIMENTAL ANIMALS 6 EXPERIMENTAL PROCEDURES 6 SALINE ACCLIMATION 7 COLLECTION AND HANDLING OF SAMPLES 7 ANALYTICAL PROCEDURES 8 ION CONCENTRATIONS AND OSMOLALITY 8 EXTRACTION OF PLASMA 9 RADIOIMMUNOASSAY OF ARGININE VASOTOCIN 10 RADIOIMMUNOASSAY OF ANGIOTENSIN I I 12 TOTAL BODY WATER 14 RESULTS 16 BODY MASS 16 HEMATOCRIT 16 PLASMA SODIUM CONCENTRATION 19 PLASMA POTASSIUM CONCENTRATION 19 PLASMA CHLORIDE CONCENTRATION 20 PLASMA OSMOLALITY 20 PLASMA AVT CONCENTRATION 23 i v PLASMA ANG I I CONCENTRATION 23 TOTAL BODY WATER 25 DISCUSSION 27 BODY MASS 27 HEMATOCRIT 28 PLASMA IONIC CONCENTRATIONS AND OSMOLALITY 28 PLASMA AVT CONCENTRATION 3 0 PLASMA ANG I I CONCENTRATION 39 PLASMA AVT AND ANG I I CONCENTRATIONS IN MALE AND FEMALE DUCKS AND GEESE 47 TOTAL BODY WATER 48 CONCLUSIONS 52 APPENDIX 54 REFERENCES 57 V LIST OF TABLES TABLE I. Mean body mass (g + se) , h e m a t o c r i t (Hct, % + se) , plasma i o n i c (mM + se) and osmotic (Osmpl, mOsm/1 + se) c o n c e n t r a t i o n s and a r g i n i n e v a s o t o c i n (AVT) and a n g i o t e n s i n I I (Ang I I , pg/ml + se) c o n c e n t r a t i o n s o f Pekin ducks, Canada geese and Glaucous-winged g u l l s d r i n k i n g f r e s h water ... 17 TABLE I I . Mean body mass (g + se) and h e m a t o c r i t (% + se) of female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s d u r i n g s a l i n e a c c l i m a t i o n 18 TABLE I I I . Mean plasma sodium and c h l o r i d e c o n c e n t r a t i o n (mM + se) and mean plasma o s m o l a l i t y (mOsm/1 + se) of female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s d u r i n g s a l i n e a c c l i m a t i o n 21 TABLE IV. Mean plasma a n t i d i u r e t i c hormone (AVT) and a n g i o t e n s i n I I (Ang II) c o n c e n t r a t i o n (pg/ml + se) of female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s d u r i n g s a l i n e a c c l i m a t i o n 24 TABLE V. Mean t o t a l body water (% body mass + se) o f female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s d u r i n g s a l i n e a c c l i m a t i o n 26 v i TABLE VI. Plasma a n t i d i u r e t i c hormone c o n c e n t r a t i o n i n mammals ( a r g i n i n e v a s o p r e s s i n , AVP) and b i r d s ( a r g i n i n e v a s o t o c i n , AVT) d r i n k i n g f r e s h water 37 TABLE V I I . R e l a t i o n s h i p o f plasma a r g i n i n e v a s o t o c i n ([AVT] p l) t o plasma o s m o l a l i t y (Osmpl) i n female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s d u r i n g s a l i n e a c c l i m a t i o n 40 TABLE V I I I . Plasma a n g i o t e n s i n I I c o n c e n t r a t i o n i n mammals and b i r d s d r i n k i n g f r e s h water 41 v i i LIST OF FIGURES FIGURE 1. The mean plasma a n t i d i u r e t i c hormone (AVT) and a n g i o t e n s i n I I (Ang II) c o n c e n t r a t i o n s , plasma o s m o l a l i t y , h e m a t o c r i t and body mass of male and female Pekin ducks d u r i n g slow s a l i n e a c c l i m a t i o n . V e r t i c a l bars i n d i c a t e + one standard e r r o r 31 FIGURE 2. The mean plasma a n t i d i u r e t i c hormone (AVT) and a n g i o t e n s i n I I (Ang II) c o n c e n t r a t i o n s , plasma o s m o l a l i t y , h e m a t o c r i t and body mass of male and female Canada geese d u r i n g slow s a l i n e a c c l i m a t i o n . V e r t i c a l bars i n d i c a t e + one sta n d a r d e r r o r 3 3 FIGURE 3. The mean plasma a n t i d i u r e t i c hormone (AVT) and a n g i o t e n s i n I I (Ang II) c o n c e n t r a t i o n s , o s m o l a l i t y , h e m a t o c r i t and body mass of Glaucous-winged g u l l s d u r i n g slow s a l i n e a c c l i m a t i o n . V e r t i c a l bars i n d i c a t e + one standar d e r r o r 35 v i i i LIST OF ABBREVIATIONS Ang I I A n g i o t e n s i n I I AVP A r g i n i n e v a s o p r e s s i n AVT A r g i n i n e v a s o t o c i n ANF A t r i a l n a t r i u r e t i c f a c t o r BSA Bovine serum albumin ECF E x t r a c e l l u l a r f l u i d ECFV E x t r a c e l l u l a r f l u i d volume GFR Glomerular f i l t r a t i o n r a t e Hct Hematocrit MT Mammalian-type nephrons NMS Neomycin s u l p h a t e [Ang I I ] p l Plasma a n g i o t e n s i n I I c o n c e n t r a t i o n [AVT] p l Plasma a r g i n i n e v a s o t o c i n c o n c e n t r a t i o n t C 1 " ] p l Plasma c h l o r i d e c o n c e n t r a t i o n Osm„. pi Plasma o s m o l a l i t y Plasma potassium c o n c e n t r a t i o n PRA Plasma r e n i n a c t i v i t y Plasma sodium c o n c e n t r a t i o n RIA Radioimmunoassay RAS R e n i n - a n g i o t e n s i n system RT R e p t i l i a n - t y p e nephrons SGS S a l t g l a n d s e c r e t i o n TBW T o t a l body water TFA T r i f l u o r o a c e t i c a c i d i x ACKNOWLE DGEMENTS Dr. Maryanne R. Hughes p r o v i d e d i n v a l u a b l e a s s i s t a n c e d u r i n g the r e s e a r c h and i n the p r e p a r a t i o n o f t h i s t h e s i s . The antiserum a g a i n s t a v i a n a n g i o t e n s i n I I (code Al/9) was k i n d l y p r o v i d e d by Dr. David A. Gray, Max-Plank I n s t i t u t , West Germany. Dr. Nadine Wilson, UBC, Dept. of Ph y s i o l o g y , p r o v i d e d the antiserum a g a i n s t a r g i n i n e v a s o t o c i n and the program 2 32-COM (Inf o m a t i c a Information Systems, Vancouver, BC) f o r hormone data r e d u c t i o n . The a s s i s t a n c e o f David Kojwang, C l a u d i a K a s s e r r a , M i c h e l l e Doering, D a n i e l Bong and Sharon Fong d u r i n g sampling s e s s i o n s i s g r e a t l y a p p r e c i a t e d . Ronnie Y a k o l e f f , M . Sc, and L e t h i k a Raveendran, M.Sc, taught me a l l I know about RIA tec h n i q u e s . T h i s r e s e a r c h was supported by Grant A-3442 from the N a t u r a l S c i e n c e s and E n g i n e e r i n g Research C o u n c i l of Canada t o Dr. Maryanne R. Hughes and by a s c h o l a r s h i p (reg. 54971) from Consejo N a c i o n a l de C i e n c i a y T e c n o l o g i a , Mexico. x I N T R O D U C T I O N B i r d s i n h a b i t i n g d e s e r t s and o c e a n i c areas have the problem of o b t a i n i n g s u f f i c i e n t o s m o t i c a l l y f r e e water t o balance water l o s t i n r e s p i r a t i o n , t h e r m o r e g u l a t i o n , and e x c r e t i o n . They u s u a l l y f a c e the a d d i t i o n a l problem of e l i m i n a t i n g e x c e s s i v e o s m o t i c a l l y a c t i v e m a t e r i a l i n g e s t e d w i t h s a l t water and s a l t - r i c h food. T e r r e s t r i a l b i r d s , l i k e mammals, r e l y on t h e i r kidneys as the s o l e r o u t e f o r s a l t e x c r e t i o n . However, the a v i a n kidney i s unable t o form a v e r y c o n c e n t r a t e d u r i n e . I t i s composed l a r g e l y of r e p t i l i a n type (RT) nephrons and the few mammalian type (MT) nephrons w i t h loops of Henle are not arranged as r e q u i r e d f o r formation of c o n c e n t r a t e d u r i n e (Braun and D a n t z l e r , 1972, 1974). Marine b i r d s , some d e s e r t b i r d s , and r a p t o r s have e v o l v e d an a c c e s s o r y e x c r e t o r y system, the n a s a l s a l t glands, which s e c r e t e i n g e s t e d s a l t i n a s m a l l e r volume o f water than was absorbed w i t h i t (Schmidt-Nielsen, e t a l . , 1958). S a l t g l a n d s e c r e t i o n (SGS) may be s t i m u l a t e d by e l e v a t e d plasma o s m o l a l i t y (Osmpl, Gray and Simon, 1985), expansion of the e x t r a c e l l u l a r f l u i d volume (ECFV, , Ruch and Hughes, 1975; Zucker, e t a l . , 1977; Hammel, e t a l . , 1980; Hughes, 1989a, b ) , h i g h p r o t e i n d i e t (Cade and Greenwald, 19 66) and d e h y d r a t i o n (Stewart, 1972). S p e c i e s w i t h s a l t glands tend t o have h i g h e r g l o m e r u l a r f i l t r a t i o n r a t e s (GFR) than s p e c i e s which l a c k s a l t glands 1 (Skadhauge, 1975; Hughes, e t a l . , 1987) and, as d r i n k i n g water s a l i n i t y i n c r e a s e s , they e i t h e r m a i n t a i n (Pekin ducks, Anas  p l a t y r h y n c h o s , Holmes, e t a l . , 1968; Hughes, 1980) or i n c r e a s e GFR ( g u l l s , Larus q l a u c e s c e n s . and Canada geese, Branta  canadensis, Hughes, 1980). In c o n t r a s t , t e r r e s t r i a l b i r d s decrease GFR (Braun and D a n t z l e r , 1972). T h i s suggests t h a t d u r i n g h i g h s a l t i n t a k e the s a l t glands produce s u f f i c i e n t f r e e water t o a l l o w the kidneys t o co n t i n u e f i l t e r i n g a t a h i g h r a t e . The osmoregulatory p e p t i d e s a n t i d i u r e t i c hormone ( 8Arg-v a s o t o c i n , AVT, appendix F i g . 1) and a n g i o t e n s i n I I ( 5 V a l -A n g i o t e n s i n I I , Ang I I , appendix F i g . 2) p l a y important r o l e s i n f l u i d homeostasis. The r e l e a s e o f AVT i s s t i m u l a t e d by o v i p o s i t i o n (Arad and Skadhauge, 1984), decreased ECFV, i n c r e a s e d Osmpl, and i n c r e a s e d plasma c o n c e n t r a t i o n o f Ang I I ([Ang H ] p l ; Erbe, e t a l . , 1985; Goto, e t a l . , 1986; Koike, 1989) , although the r o l e o f Ang I I i s s t i l l e q u i v o c a l (Gray and Simon, 1985; Gray, e t a l . , 1986). Among the f a c t o r s c o n t r o l l i n g Ang I I r e l e a s e i n b i r d s are decreased ECFV and i n c r e a s e d plasma t o n i c i t y (Gray and Simon, 1985, 1987; Gray, 1987), i n c r e a s e d plasma sodium c o n c e n t r a t i o n ( [ N a + ] p l , Reid, 1984; Nishimura, e t a l . , 1984; Erbe, e t a l . , 1988), and decreased b l o o d p r e s s u r e (Nishimura, e t a l . , 1984; Wilson, e t a l . , 1985). Most r e s e a r c h e r s agree t h a t a v i a n [AVT] p l i s mainly c o n t r o l l e d by ECF t o n i c i t y and [Ang I I ] p l by ECFV (Simon and Gray, 1989), as i n mammals (Maebashi and Yashinaga, 1967; 2 Gordon and Pawsey, 1971; Dunn, e t a l . , 1973; Robertson, e t a l . , 1977; Wade, e t a l . , 1982). In b i r d s i n c r e a s e d [AVT] p l decreased p e r f u s i o n of RT nephrons (Braun and D a n t z l e r , 1974; 1984) and i n c r e a s e d r e a b s o r p t i o n of water i n the c o l l e c t i n g duct ( S t a l l o n e and Braun, 1985), both mechanisms t h a t conserve body water (Raveendran, 1987; Gray and Simon, 1983, 1987; Gray and Erasmus, 1988, 1989; D a n t z l e r , 1989). E l e v a t e d [Ang I I ] p l s t i m u l a t e d d r i n k i n g (Kaufman and P e t e r s , 1980; F i t z s i m o n s , e t a l . , 1982; T a k e i , e t a l . , 1985), d i u r e s i s (Thomas and Skadhauge, 1985; Wilson, e t a l . , 1985; Gray and Simon, 1985), n a t r i u r e s i s ( S t a l l o n e and Nishimura, 1985), and a l d o s t e r o n e r e l e a s e (Hollander, 1971). Blood p r e s s u r e may be r a i s e d by Ang I I e i t h e r d i r e c t l y (Moore, e t a l . , 1981; Nakamura, e t a l . , 1982; Wilson and West, 1986) or i n d i r e c t l y by s t i m u l a t i n g r e l e a s e of catecholamines (Nishimura, e t a l . , 1981b; Wilson and B u t l e r , 1983a, b ) . I n t r a c e r e b r o v e n t r i c u l a r i n j e c t i o n s of Ang I I i n h i b i t e d duck SGS e l i c i t e d by i n t r a v e n o u s ( i v ) i n f u s i o n of h y p e r t o n i c s a l i n e (Gerstberger, e t a l . , 1984). The e f f e c t s o f AVT and Ang I I on GFR, SGS, and d r i n k i n g w i l l o b v i o u s l y a f f e c t a b i r d ' s t o t a l body water (TBW) and water f l u x . Volume and Na + d e p l e t i o n e l e v a t e d [Ang H ] p l and [AVT] p l, r e s p e c t i v e l y (Erbe, e t a l . , 1985) and enhanced r e n a l water and s a l t r e a b s o r p t i o n (presumably v i a a l d o s t e r o n e ) i n c o n d i t i o n s o f s a l t s t r e s s (Simon and Gray, 1989). 3 Most o f our c u r r e n t understanding o f osmoregulation i n b i r d s w i t h s a l t glands has been gained from s a l i n e i n f u s i o n experiments on domestic ducks, geese and g u l l s . The r o u t e by which s a l t i s a d m i n i s t e r e d t o a b i r d seems t o i n f l u e n c e changes i n ECF volume and t o n i c i t y , thereby a f f e c t i n g [AVT] p l and [Ang H ] p l / and the r e s u l t a n t s a l t g l a n d and kidney f u n c t i o n . Intravenous i n f u s i o n o f c o n c e n t r a t e d NaCl i n t o ducks s t i m u l a t e d SGS and i n h i b i t e d c l o a c a l e x c r e t i o n , but i v i n f u s i o n o f d i l u t e s a l i n e favoured c l o a c a l f l u i d (urine) p r o d u c t i o n (Simon-Oppermann, e t a l . , 1984). I n t r a p e r i t o n e a l i n j e c t i o n o f NaCl s i g n i f i c a n t l y i n c r e a s e d [Na +] p l i n both ducks and g u l l s but s t i m u l a t e d s a l t g l a n d s e c r e t i o n o n l y i n g u l l s , which a l s o i n c r e a s e d ECFV (Hughes, 1989a). When g u l l s drank s a l i n e and NaCl en t e r e d the ECF v i a the i n t e s t i n a l t r a c t , both s a l t glands and kidneys continued t o work i n c o n c e r t (Walter and Hughes, unpubl) and hem a t o c r i t (Hct) was u n a l t e r e d , s u g g e s t i n g t h a t plasma volume was maintained (Roberts and Hughes, 1984). In ducks a c c l i m a t e d t o e i t h e r f r e s h water o r 2 % s a l i n e , [Ang H ] p l was p o s i t i v e l y c o r r e l a t e d w i t h Osmpl (Gray and Simon, 1984, 1985), but [AVT] p l and [Ang H ] p l i n b i r d s d u r i n g changes i n s e l f - r e g u l a t e d s a l t i n t a k e a re unknown. To assess whether the changes i n plasma i o n i c c o n c e n t r a t i o n s , Hct, Osmpt, [AVT] p l and [Ang H ] p t observed a f t e r i v NaCl i n f u s i o n a c c u r a t e l y r e f l e c t changes a s s o c i a t e d w i t h i n c r e a s e d NaCl i n g e s t i o n , these parameters were measured 4 i n P e kin ducks, Canada geese, and Glaucous-winged g u l l s d u r i n g slow a c c l i m a t i o n t o s a l i n e d r i n k i n g water. The hypotheses t e s t e d were t h a t d u r i n g slow s a l t a c c l i m a t i o n : (1) plasma i o n i c c o n c e n t r a t i o n and ECFV remain unchanged as l o n g as b i r d s e x c r e t e excess s a l t without l o s i n g body water, (2) based on the r e l a t i v e e f f i c i e n c y o f t h e i r s a l t glands t o s e c r e t e NaCl, plasma i o n i c c o n c e n t r a t i o n s i n c r e a s e and ECFV decreases f i r s t i n ducks, second i n geese and l a s t i n g u l l s , (3) the [AVT] p l i s i n c r e a s e d by i n c r e a s e d ECF t o n i c i t y , (4) the [Ang i s i n c r e a s e d by decreased ECFV. 5 MATERIALS AND METHODS Experimental Animals: S i x male and 7 female a d u l t Pekin Ducks (Anas  p l a t y r h y n c h o s ) , and 4 female and 6 male a d u l t Canada Geese (Branta canadensis) were s t u d i e d . Blood samples were o b t a i n e d from 4 Glaucous-winged G u l l s (Larus cdaucescens) d u r i n g another s a l t a c c l i m a t i o n study. Ducks and geese had been hatched and r e a r e d a t the U n i v e r s i t y o f B r i t i s h Columbia South Campus Animal Care F a c i l i t y . They were f e d dry l a y i n g p e l l e t s ( B u c k e r f i e l d s L t d , A b b o t t s f o r d , BC; Na +, 68 mEq/kg; K*, 145 mEq/kg; CI", 190 mEq/kg, Hughes, 1980; water content, 12.7 + 0.1 %) . G u l l s had been c o l l e c t e d as n e s t l i n g s on C h r i s t i e I s l e t , i n Howe Sound, BC and were f e d b a i t h e r r i n g (Clupea p a l a s i i ; Na +, 82 mEq/1; 124 mEq/1; CI", 69 mEq/1, Hughes, 1972) supplemented w i t h a l i q u i d v i t a m i n mixture (Paramette, A y e r s t L a b o r a t o r i e s , M ontreal, PQ). During the experimental p e r i o d , a l l b i r d s were housed i n p a r t i a l l y covered (5 x 2 x 3.5 m) outdoor e n c l o s u r e s a t the UBC South Campus Animal Care F a c i l i t y . E x perimental Procedures: The c a p t u r e , h a n d l i n g , and sampling procedures were s i m u l a t e d s e v e r a l times b e f o r e the experiments were undertaken t o reduce a r t i f a c t s due t o s t r e s s . The p r o t o c o l was designed i n accordance w i t h g u i d e l i n e s s e t f o r t h by the Canadian 6 C o u n c i l on Animal Care. S a l i n e A c c l i m a t i o n ; The b i r d s were pre s e n t e d w i t h i n c r e a s i n g l y c o n c e n t r a t e d NaCl s o l u t i o n s (prepared f r e s h d a i l y ) i n p l a s t i c wading p o o l s (20 g a l ) . The ducks were a c c l i m a t e d t o 3 00 mM NaCl i n 4 equal weekly increments, and maintained a t t h i s c o n c e n t r a t i o n f o r 3 weeks. Ducks l o s t weight when g i v e n 375 mM NaCl t o d r i n k f o r one week. Blood samples were taken and ducks were r e t u r n e d t o 3 00 mM NaCl f o r one week. Then the d r i n k i n g water was i n c r e a s e d t o 450 mM NaCl ( e q u i v a l e n t t o the sodium c o n c e n t r a t i o n o f f u l l s t r e n g t h sea water) f o r one week. The geese were a c c l i m a t e d t o 450 mM NaCl i n 6 equal weekly increments. The g u l l s (which had a temperature monitor implanted i n the p e r i t o n e a l c a v i t y ) were a c c l i m a t e d t o 375 mM NaCl i n 4 equal weekly increments. C o l l e c t i o n and Handling of Samples: At the end of every a c c l i m a t i o n p e r i o d the b i r d s were f a s t e d 18 hours and weighed u s i n g a C h a t i l l o n s p r i n g balance (Model IN-12, ITN, M i s s i s a u g a , ON). A b l o o d sample (0.5 ml) was taken from a l e g v e i n i n t o a h e p a r i n i z e d s y r i n g e and t r a n s f e r r e d i n t o a 1.5 ml Eppendorf c e n t r i f u g e tube. T r i p l i c a t e Strumia microhematocrit (Hct) tubes were immediately f i l l e d . Blood and Hct tubes were c e n t r i f u g e d (Eppendorf C e n t r i f u g e , Model 5412, Brinkmann Instruments Inc, 7 Westbury, NY) a t 15,600 x g f o r 3 min. The plasma was decanted; Osmpl was immediately determined; and the remaining plasma was s t o r e d a t 4°C. For hormone a n a l y s i s , a b l o o d sample (5.0 ml) was taken i n t o a n o n - h e p a r i n i z e d s y r i n g e , t r a n s f e r r e d t o a c h i l l e d p o l y p r o p y l e n e tube c o n t a i n i n g 70 u l 0.125 M EDTA (#6450, V a c u t a i n e r , Becton-Dickinson Canada L t d ) , and c e n t r i f u g e d ( O r b i t C e n t r i f u g e , Model 807, P h i l l i p s - D r u c k e r , A s t o r i a , OR) a t 4,000 x g a t 4°C f o r 10 min. Plasma was s e p a r a t e d i n t o two equal f r a c t i o n s , t o one of which 100 u l 0.02 5 M o-p h e n a n t h r o l i n e (#P-9375, Sigma Chemicals, St L o u i s , MO) was added as an a n g i o t e n s i n c o n v e r t i n g enzyme i n h i b i t o r ( D u s t e r d i e c k and McElwee, 1971). Both f r a c t i o n s were s t o r e d a t -20°C u n t i l e x t r a c t i o n f o r radioimmunoassay (RIA). A n a l y t i c a l Procedures; Ion C o n c e n t r a t i o n s and O s m o l a l i t y : D u p l i c a t e 2 0 u l plasma a l i q u a n t s were an a l y z e d f o r sodium ([Na +] p l) and potassium ( [ K + ] p l ) c o n c e n t r a t i o n s u s i n g an I n t e r n a l s t a n d a r d flame photometer (Model I L 943, I n s t r u m e n t a t i o n Laboratory, SpA, Milano, I t a l y ) . Plasma c h l o r i d e c o n c e n t r a t i o n ( [ C l " ] p l ) was determined on d u p l i c a t e 10 u l a l i q u a n t s by e l e c t r o m e t r i c t i t r a t i o n w i t h a B u c h l e r d i g i t a l c h l o r i d o m e t e r (Model 42500, Buchler Instruments Inc, F o r t Lee, NY) . Plasma o s m o l a l i t y (Osmpl) was measured on t r i p l i c a t e 10 u l plasma a l i q u a n t s u s i n g a Wescor vapour p r e s s u r e osmometer 8 (Model 5500, Wescor Inc, Logan, UT). E x t r a c t i o n of Plasma: Hormones were e x t r a c t e d from plasma samples by a d s o r p t i o n t o prepacked o c t a d e c a s i l y l - s i l i c a c a r t r i d g e s (Sep-Pak C 1 8 Waters, M i l f o r d , MA) a c c o r d i n g t o a method adapted from H a r t t e r (1986). Each c a r t r i d g e was used f o r o n l y one plasma sample and b e f o r e use was s e q u e n t i a l l y washed w i t h 4 ml 100 % methanol ( g l a s s d i s t i l l e d , OmniSolv, BDH Chemicals, #B-90234, Toronto, ON); 4 ml 0.5 % t r i f l u o r o a c e t i c a c i d (TFA, HPLC/ Spec t r o Grade, Sigma Chemicals, #T-1647, St L o u i s , MO) i n 90 % methanol and 8 ml d i s t i l l e d water. Then a measured volume ( u s u a l l y 1.0 ml) of thawed plasma was s l o w l y (over 1 min) passed through, and the c a r t r i d g e was r i n s e d w i t h 8 ml d i s t i l l e d water. The hormones were e l u t e d w i t h 3.4 ml 90 % methanol-0.5 % TFA. The e l u a t e s were d r i e d i n a vacuum ev a p o r a t o r (Speed Vac Concentrator, Savant, New York, NY) and s t o r e d a t -20°C f o r RIA the next day. Immediately b e f o r e RIA the plasma samples were r e c o n s t i t u t e d w i t h s u f f i c i e n t b u f f e r t o a c h i e v e a hormone c o n c e n t r a t i o n t h a t should f a l l on the l i n e a r p o r t i o n of the standard curve, i e . , the area of g r e a t e s t accuracy. Q u a l i t y c o n t r o l samples (from a pooled plasma supply) were e x t r a c t e d and t r e a t e d as experimental samples. 9 Radioimmunoassay of A r g i n i n e V a s o t o c i n : An antibody a g a i n s t fowl AVT, which d i d not c r o s s - r e a c t w i t h o x y t o c i n or mesotocin (Raveendran, 1987), was r a i s e d i n guinea p i g s u s i n g the method of Herbert (1973). The AVT was i o d i n a t e d u s i n g the method f o r AVP (Ledsome, e t a l . , 1982). S y n t h e t i c fowl AVT (10 ug; #V-0130, Sigma, Chemicals, St L o u i s , MO) was d i s s o l v e d i n 10 u l 0.05 M a c e t i c a c i d (#AC5003-78, BDH, Toronto, ON), and 20 u l phosphate b u f f e r (0.5 M, pH 7.4) were added t o the s o l u t i o n . To t h i s , 10 u l chloramine T (1 mg/ml; #1022 l o t 1A2, Eastman, Kodak, Co, Rochester, NY), and 15 u l o f Na 1 2 5I (IMS. 30, Amersham Radiochemicals, O a k v i l l e , ON) were added i n r a p i d s u c c e s s i o n . The r e a c t i o n was allowed t o proceed f o r 50 s b e f o r e 100 u l bovine serum albumin (BSA, #A-87 63, Sigma Chemicals, St L o u i s , MO) i n i s o t o n i c s a l i n e (250 mg BSA/ml) were added, f o l l o w e d by 50 mg AGI-X10 (#9995, B i o r a d , M i s s i s a u g a , ON) i n 200 u l d i s t i l l e d water. The mixture was c e n t r i f u g e d f o r 3 min and the supernatant f l u i d was t r a n s f e r r e d t o a CM Sephadex C-25 column (Pharmacia, Upsala, Sweden) a t 4°C. I o d i n a t e d AVT was e l u t e d from the column a t a flow r a t e o f 0.72 ml/min u s i n g 0.6 M a c e t a t e b u f f e r (pH 4.85) . The s p e c i f i c r a d i o a c t i v i t y of i o d i n a t e d p e p t i d e was c a l c u l a t e d u s i n g the s e l f - d i s p l a c e m e n t method of M o r r i s (1976). Monoiodinated p e p t i d e was s t o r e d i n p l a s t i c tubes a t 4°C and used f o r up t o 6 weeks. For each RIA, tubes c o n t a i n i n g AVT (100 u l ) i n c o n c e n t r a t i o n s r a n g i n g from 5 t o 1000 pg/ml were prepared from 10 a s e p a r a t e l y f r o z e n (-20°C) a l i q u o t o f the AVT s t o c k s t a n d a r d s o l u t i o n (50 ng/ml 0.1 M a c e t i c a c i d ; #V-0130, Sigma, Chemicals, S t L o u i s , MO) i n RIA b u f f e r c o n t a i n i n g 0.1 % BSA. Then 100 u l of the antiserum, d i l u t e d w i t h RIA b u f f e r (0.15 M phosphate, pH 7.2), were added t o each tube f o r a f i n a l a n t i b o d y d i l u t i o n of 1:100,000. A l l tubes were made up t o 900 u l w i t h RIA b u f f e r , mixed and incubated f o r 48 h a t 4°C. Then 50 u l monoiodo-AVT (approx 2,000 cpm) were added t o each tube ( f i n a l i n c u b a t i o n volume 950 u l ) . The tubes were w e l l mixed and i n c u b a t e d f o r a f u r t h e r 96 h a t 4°C. A l l RIA procedures were c a r r i e d out i n s i l i c o n i z e d g l a s s tubes kept i n i c e . Tubes c o n t a i n i n g t r a c e r and b u f f e r alone ( n o n - s p e c i f i c b i n d i n g ) ; t r a c e r , antibody and b u f f e r (maximum b i n d i n g o f t r a c e r t o the antibody i n absence of c o m p e t i t i o n ) , and standards were analyzed i n t r i p l i c a t e . Plasma samples were ana l y z e d i n t r i p l i c a t e f o r s p e c i f i c b i n d i n g ( t r a c e r , b u f f e r , plasma e x t r a c t and antibody) and i n d u p l i c a t e f o r n o n - s p e c i f i c b i n d i n g ( t r a c e r , b u f f e r and plasma e x t r a c t ) . To s e p a r a t e hormone bound t o antibody from f r e e hormone, 2 50 u l o f a charcoal-BSA suspension (4 g c h a r c o a l N o r i t A; Lot #733195, F i s h e r Chemicals, Toronto, ON, i n 500 ml 0.2 M phosphate b u f f e r , pH 7.4 w i t h 800 mg BSA) were added t o each tube (Nishimura, e t a l . , 1981a; Uyehara and Claybaugh, 1988). The tube c o n t e n t s were w e l l mixed and c e n t r i f u g e d a t 2,200 x g f o r 3 0 min a t 4°C. A l l the supernatant f l u i d (bound hormone) was decanted i n t o a c l e a n tube and i t s r a d i o a c t i v i t y was counted s e p a r a t e l y from t h a t o f the c h a r c o a l p e l l e t ( f r e e hormone) u s i n g an Autommatic gamma counter (LKB Clinigamma 1272, Upsala, Sweden). Data r e d u c t i o n was performed u s i n g the program 232-COM (Infomatica I n f o r m a t i o n Systems, Vancouver, BC) . Radioimmunoassay of A n g i o t e n s i n I I : The antibody a g a i n s t fowl Ang I I was r a i s e d i n r a b b i t s (Gray, 1987) u s i n g a m o d i f i c a t i o n o f the method o f Sofroniew, e t a l . , (1978). I o d i n a t i o n and RIA of Ang I I was performed f o l l o w i n g a m o d i f i c a t i o n o f the method of Gray and Simon (1984, 1985) . The main changes were the use of a h i g h e r m o l a r i t y phosphate b u f f e r (0.5 M vs 0.2 M) and lo n g e r r e a c t i o n time (30 sec vs 10 sec) f o r i o d i n a t i o n , and the s e p a r a t i o n o f bound from f r e e hormone u s i n g a charcoal-BSA suspension i n s t e a d o f a b s o l u t e a l c o h o l . S y n t h e t i c fowl Ang I I , 1Asp- 5Val Ang I I , (#7005, P e n i n s u l a L a b o r a t o r i e s Inc, Belmont, CA) was l a b e l e d w i t h 1 2 5 I u s i n g the chloramine T method (Hunter and Greenwood, 1962). To the s y n t h e t i c Ang I I (10 ug) d i s s o l v e d i n 10 u l a c e t i c a c i d (0.1 M) , 10 u l phosphate b u f f e r (0.5 M, pH 7.4) were added. To t h i s , 1 mCi Na 1 2 5I and 2 0 u l of chloramine T s o l u t i o n (2 mg/ml phosphate b u f f e r ) were added i n r a p i d s u c c e s s i o n and the mixture was incubated f o r 30 seconds. The r e a c t i o n was ter m i n a t e d by the a d d i t i o n of 100 u l sodium m e t a b i s u l f i t e (2.5 mg/ml phosphate b u f f e r , #5X630, MCB, USA) and 500 u l RIA 12 b u f f e r . The RIA b u f f e r was composed of 0.1 M T r i s (pH 7.4; T r i s Base Sigma Chemicals, #T-1503, St L o u i s , MO) w i t h 3 % BSA and 2 % neomycin s u l f a t e (NMS, #N-1876, Sigma, Chemicals, St L o u i s , MO). The t r a c e r was p u r i f i e d by column chromatography on DEAE-Sephadex A-25 (Pharmacia, Upsala, Sweden; D u s t e r d i e c k and McElwee, 1971). I o d i n a t e d Ang I I was s e p a r a t e d from non-i o d i n a t e d p e p t i d e on a double column system (column I, 10 x 300 mm; column I I , 7 x 300 mm) e q u i l i b r a t e d w i t h RIA b u f f e r . The s p e c i f i c r a d i o a c t i v i t y of i o d i n a t e d p e p t i d e was c a l c u l a t e d u s i n g the s e l f - d i s p l a c e m e n t method of M o r r i s (1976). For each RIA, tubes c o n t a i n i n g Ang I I (200 u l ) i n c o n c e n t r a t i o n s r a n g i n g from 0.5 t o 500 pg/ml were prepared from a s e p a r a t e l y f r o z e n (-20°C) a l i q u o t o f the Ang I I s t o c k s t a n d a r d s o l u t i o n (50 ng/ml 0.1 M a c e t i c a c i d ; #7005, P e n i n s u l a L a b o r a t o r i e s Inc, Belmont, CA) i n RIA b u f f e r . Then 2 00 u l o f the antiserum (code Al/9) were added t o each tube f o r a f i n a l d i l u t i o n of 1:30,000. Samples (200 u l ) were t r e a t e d i n the same way. The assay mixtures were incubated a t 4°C f o r 48 h. Then, 50 u l (approx 2,500 cpm) o f monoiodinated Ang I I were added t o each tube and incubated f o r an a d d i t i o n a l 24 h a t 4°C. A l l RIA procedures were c a r r i e d out i n s i l i c o n i z e d g l a s s tubes kept i n i c e . N o n - s p e c i f i c b i n d i n g , maximum b i n d i n g and standards were analyzed i n t r i p l i c a t e . Plasma samples were an a l y z e d i n t r i p l i c a t e f o r s p e c i f i c b i n d i n g and i n d u p l i c a t e f o r n o n - s p e c i f i c b i n d i n g . S e p a r a t i o n of hormone bound t o 13 a n t i b o d y from f r e e hormone was achieved u s i n g the charcoal-BSA method, as d e s c r i b e d f o r AVT; r a d i o a c t i v i t y o f the bound and f r e e hormone was counted s e p a r a t e l y and data r e d u c t i o n was performed u s i n g the program 232-COM. T o t a l Body Water: The TBW was determined from plasma disappearance curves f o l l o w i n g t he i n j e c t i o n o f 3H 20 (New England N u c l e a r Corp, Canada) i n i s o t o n i c s a l i n e . The TBW was determined when b i r d s were d r i n k i n g f r e s h water and a f t e r a c c l i m a t i o n t o 300 mM NaCl (ducks and geese), o r 375 mM NaCl ( g u l l s ) . The b i r d s were f a s t e d o v e r n i g h t and t h e i r d r i n k i n g water was removed one hour b e f o r e each b i r d was weighed and i n j e c t e d i n a l e g v e i n w i t h 3H 20 ( f r e s h water and s a l i n e a c c l i m a t e d ducks 13 u C i and 22 u C i , r e s p e c t i v e l y ; geese 130 u C i and 15 u C i , r e s p e c t i v e l y ; and g u l l s 8 u C i and 15 u C i , r e s p e c t i v e l y ) . The i n j e c t a t e volume was determined by weighing the s y r i n g e s b e f o r e and a f t e r i n j e c t i o n assuming 1 ml equal t o 1 g. The end of the i n j e c t i o n was taken as time 0. The b i r d was r e t u r n e d t o i t s e n c l o s u r e (without water) . E q u i l i b r a t i o n time f o r i n t r a v e n o u s l y i n j e c t e d 3H 20 had been determined t o be 30 min or l e s s i n the Glaucous-winged g u l l (Hughes, e t a l . , 1987) and Canada geese (Hughes, Kojwang and Zenteno S a v i n , unpubl). A f t e r one hour, timed u s i n g a c o n t i n u o u s l y r e c o r d i n g C a s i o e l e c t r o n i c c l o c k (Chromatographic S p e c i a l i t i e s LTD, B r o o k l i n e , ON), each b i r d was r e c a p t u r e d and a 1.0 ml b l o o d sample was 14 drawn from the c o n t r a l a t e r a l l e g i n t o a h e p a r i n i z e d s y r i n g e . To determine r a d i o a c t i v i t y (3H) t e n 10 u l i n j e c t a t e a l i q u a n t s and d u p l i c a t e 50 u l plasma a l i q u a n t s were p l a c e d i n t o 10 ml of Aquasol-2 s c i n t i l l a t i o n f l u i d (Dupont NEN, D o r v a l , PQ) and counted i n a l i q u i d s c i n t i l l a t i o n counter (Beckman LS 9000 m i c r o p r o c e s s o r c o n t r o l l e d ) . Plasma i s o t o p e c o n c e n t r a t i o n , expressed as d i s i n t e g r a t i o n s per minute (DPM/min), was conv e r t e d t o DPM/ml water by d i v i d i n g i t by the percentage of water i n the plasma, as determined by d r y i n g weighed plasma a l i q u a n t s t o c o n s t a n t weight a t 100°C. The percentage of water i n the plasma of b i r d s a c c l i m a t e d t o f r e s h water or 3 00 mM NaCl was as f o l l o w s , ducks: 93.0 ± 0.6 % (n=4) , and 93.9 + 0.1 % (n=12) , r e s p e c t i v e l y ; geese: 93.6 + 0.3 % (n=10) , and 93.1 + 0.8 % ( n = 8 ) r e s p e c t i v e l y , and g u l l s : 94.0 + 0.2 % (n=4), and 93.6 + 0.4 % (375 mM NaCl, n=4) , r e s p e c t i v e l y . The TBW was c a l c u l a t e d by d i v i d i n g the t o t a l i n j e c t e d DPM by DPM/ml body water. Data f o r s p e c i e s and sexes on f r e s h water and 450 mM NaCl regimes were compared u s i n g a n a l y s i s of v a r i a n c e (ANOVA) wit h Tukey's posthoc t e s t u s i n g a microcomputer s t a t i s t i c a l program, SYSTAT (Wilkinson, 1988). Comparisons of mean v a l u e s d u r i n g i n c r e a s e s i n d r i n k i n g water s a l i n i t y were made by p a i r e d t - t e s t s w i t h B o n f e r r o n i - a d j u s t e d c o n f i d e n c e i n t e r v a l s (where P<0.05/number of p a i r s , Shott, 1990) u s i n g SYSTAT. Data ar e g i v e n as means + standard e r r o r s and s i g n i f i c a n c e assumed i f P<0.05 (ANOVA) or i f P<0.01 ( p a i r e d t - t e s t ) . 15 R E S U L T S Body Mass: The i n i t i a l mean body mass o f Pekin ducks was lower (P<0.05) than t h a t of Canada geese and g r e a t e r (P<0.05) than t h a t o f Glaucous-winged g u l l s (Table I) . Slow s a l i n e a c c l i m a t i o n had no e f f e c t on duck body mass u n t i l b i r d s drank 450 mM NaCl, when i t tended t o decrease i n females (P<0.05) and decreased i n males (P<0.01, Ta b l e I I ) . A f t e r a c c l i m a t i o n t o s a l i n e e q u i v a l e n t t o sea water (450 mM NaCl), body mass of female (8.0 + 1.7 %, P<0.8) and male (9.7 + 1.8 %, P<0.9) geese remained unchanged (Table II) . Glaucous-winged g u l l s i n c r e a s e d (P<0.01) body mass over i n i t i a l v a l u e s when a c c l i m a t e d t o 375 mM NaCl (Table I I ) . Hematocrit: On the f r e s h water regime, ducks tended (P<0.2) t o have lower Hct than geese and g u l l s , which had the same Hct; but o n l y the d i f f e r e n c e between female ducks and female geese was s t a t i s t i c a l l y s i g n i f i c a n t (P<0.05). A c c l i m a t i o n t o s a l i n e d i d not a f f e c t Hct i n ducks u n t i l 450 mM NaCl was o f f e r e d , when Hct i n c r e a s e d i n females (P<0.005) and tended t o i n c r e a s e i n males (P<0.05, Table I I ) . The Hct i n male geese i n c r e a s e d (P<0.01) and tended t o i n c r e a s e i n females (P<0.05) when they drank 150 mM NaCl, and then g r a d u a l l y r e t u r n e d t o the f r e s h water v a l u e s as d r i n k i n g water s a l i n i t y i n c r e a s e d f u r t h e r 16 TABLE I. Mean body mass (g + se) , hematocrit (Hct, % + se) , plasma i o n i c (mM + se), osmotic (Osmpl, mOsm/1 + se) concentrations and arginine vasotocin (AVT) and angiotensin II (Ang I I , pg/ml + se) concentrations of Pekin ducks, Canada geese and Glaucous-winged g u l l s drinking fresh water. DUCKS GEESE GULLS (11=13) (n=10) (n=4) Body Mass 3036.7* ± 246.1 ± 4716.4 663.0 + 900.6 B 24 . 0 Hct + 40.8 3 . 6 ± 46.8 0.4 + 46.5 3 .1 W p i + 153 . 8 4 . 0 ± 150.4 3 . 0 + 151.0 0.6 + 2.4 0.4 ± 3 . 0 0.4 + 2.6 0.2 + 114 . 3 2.8 ± 106. 6 2.5 + 121.0A 2 . 0 Osmpl + 298.1 8.1 ± 289.7 7.2 + 294.5 3.6 AVT + 44 .1 11.1 ± 27 . 6 18.4 + 35.1 16. 1 Ang II + 41.2 32.4 ± 23.5 9 . 5 + 59. 6 12 . 5 *P<0.05, B P<0.01 Compared to geese. ANOVA. 17 TABLE I I . Mean body mass (g + se) and hematocrit (% ± se) of female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s during s a l i n e acclimation. NaCl (mM) Ducks females (n=7) 2961 + 264 75 3086 + 254 150 225 BODY MASS 3093 ± 224 3107 + 252 300 3014 + 186 375 3039 + 228 450 2536 + 409 males (n=6) 3127 - 210 3158 + 204 3133 + 221 3108 - 220 3158 + 213 3133 + 154 2683 + 194 Geese females (n=4) 4031 4105 4043 4018 3931 3825 + 490 + 617 + 640 + 709 + 717 + 709 3708 + 721 males (n=6) G u l l s 3 (n=4) 5225 900 + 24 5255 5075 5040 4958 908 + 21 4837 + 529 + 581 + 512 + 530 + 628 + 591 926* + 28 4720 + 710 Ducks females (n=7) 40.2 39.5 HEMATOCRIT 40.3 38.8 39 . 4 38 . 4 + 4.5 + 2.8 + 5.3 + 6.7 + 4.4 + 4.9 48 . 0* + 2.4 males 41.8 43.7 40.7 42.8 43.3 41.5 49.0 (n=6) ± 2.0 + 2.2 + 3.3 ± 0.8 + 2.1 + 1.8 ± 1.9 Geese females (n=4) 46.7 + 0.6 53.2 + 1.7 51. 6 + 4.2 50. 7 + 3.3 48.7 + 4.0 48.7 + 4.8 males (n=6) 46.9 + 2.8 50.7 52.0 52.3 50.6 50.2 + 2.5 + 1.6 + 2.9 + 2.1 + 1.8 Gulls'" (n=4) 46.5 + 3.1 44.9 + 1.6 44 . 9 + 2.2 47.6 + 1.6 47.7 + 1.1 P<0.01, P<0.005 Compared to fresh water values, paired t - t e s t . a G u l l s were acclimated to 112, 225, 340 and 375 nH NaCl. 18 (Table I I ) . S a l i n e a c c l i m a t i o n d i d not a f f e c t g u l l Hct (Table II) . Plasma Sodium C o n c e n t r a t i o n : The [Na +] p l was the same i n ducks, geese and g u l l s d r i n k i n g f r e s h water (Table I) . When 75 mM NaCl was g i v e n , [Na +] p l \ decreased i n female ducks (P<0.005) and tended t o decrease i n male ducks (P<0.05). In females [Na +] p l r e t u r n e d t o f r e s h water v a l u e s when 150 mM NaCl was o f f e r e d (P<0.005), then decreased a g a i n (P<0.001) when d r i n k i n g water s a l i n i t y was i n c r e a s e d t o 225 mM NaCl, and remained a t the lower v a l u e u n t i l i t tended t o i n c r e a s e i n both sexes (P<0.05) when they drank 450 mM NaCl (Table I I I ) . S a l i n e a c c l i m a t i o n d i d not a f f e c t geese [Na +] p l u n t i l 450 mM NaCl was presented (Table I I I ) . G u l l [Na +] p l i n c r e a s e d (P<0.01) when they drank 340 mM NaCl (Table I I I ) . Plasma Potassium C o n c e n t r a t i o n : The i n i t i a l [ K + ] p l of ducks, geese and g u l l s was the same (Table I ) . When b i r d s drank 450 mM NaCl, [ K + ] p l tended t o decrease i n female ducks (1.9 + 0.2 mM, P<0.05), but was not a f f e c t e d i n male ducks (2.5 + 0.7 mM, P<0.9); [K^pi w a s reduced i n both sexes of geese (females, 2.2 + 0.5 mM, P<0.01, males, 2.4 + 0.3 mM, P<0.01). G u l l [Na +] p l was unchanged (2.3 + 0.5 mM, P<0.9) by a c c l i m a t i o n t o 375 mM NaCl. 19 Plasma C h l o r i d e C o n c e n t r a t i o n : The [ C l " ] p l i n ducks d r i n k i n g f r e s h water tended t o be h i g h e r than [ C l " ] p l i n geese (P<0.3), which was lower than [ C l " ] p l i n g u l l s (P<0.05, Ta b l e I ) . In ducks [ C l " ] p l was unchanged, except f o r a t r a n s i e n t decrease when 225 mM NaCl was g i v e n (females, P<0.005, males, P<0.01); when 450 mM NaCl was o f f e r e d , [ C l " ] p l i n c r e a s e d i n male (P<0.05) but not female (P<0.5) ducks (Table I I I ) . S a l i n e a c c l i m a t i o n d i d not a f f e c t [ C l " ] p l i n geese or g u l l s (Table I I I ) . Plasma O s m o l a l i t y : I n i t i a l 0sm p l was the same i n ducks, geese and g u l l s (Table I ) . In female ducks Osmpl decreased (P<0.005) and tended t o decrease i n male ducks (P<0.05) when 75 mM NaCl was pr e s e n t e d and remained a t t h i s l e v e l (except f o r a t r a n s i e n t i n c r e a s e when 150 mM NaCl was given) u n t i l 450 mM NaCl was o f f e r e d , when i t i n c r e a s e d (P<0.005) i n both sexes. The increment i n Osmpl was s m a l l e r i n female ducks than i n males (P<0.05) when b i r d s drank 450 mM NaCl (Table I I I , F i g . 1). Except f o r a t r a n s i e n t i n c r e a s e i n Osmpl when g i v e n 225 mM NaCl ( s t a t i s t i c a l l y s i g n i f i c a n t o n l y i n males, P<0.01), female and male geese maintained f r e s h water Osmpl u n t i l i t i n c r e a s e d i n both sexes (P<0.01, Ta b l e I I I , F i g 2) when 450 mM NaCl was pres e n t e d . Glaucous-winged g u l l Osmpl i n c r e a s e d (P<0.01) when they were f i r s t p r e s e n t e d w i t h s a l i n e (112 mM NaCl, T a b l e I I I , F i g . 3) and remained, t h e r e a f t e r , unchanged. 20 TABLE I I I . Mean plasma sodium and chloride concentration (mM + se) and plasma osmolality (mOsm/1 + se) of female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s during s a l i n e acclimation. NaCl (mM) Ducks females (n=7) males (n=6) Geese females (n=4) males (n=6) G u l l s 3 (n=4) Ducks females (n=7) males (n=6) Geese females (n=4) males (n=6) G u l l s 3 (n=4) 0 75 150 225 300 PLASMA SODIUM CONCENTRATION 375 153.3 ± 4.0 154 .4 + 4.3 148.8 + 4.2 149. 6 + 2.4 151.0 + 0.6 146.1* ± 4.5 148.8 + 1.2 151. 8 + 3.1 150. 5 + 2.6 151.1 + 0.5 153.2 ± 3.2 150.0 + 2.7 153 . 0 + 2.6 152.6 + 2.0 142.9' ± 3.1 149.5 + 2.5 154.2 + 3.6 155. 0 + 4.8 153.5 + 1.6 143.9 152.8 + 4.8 + 2.8 147.6 + 1.2 150. 6 + 5.2 150.4 + 3.6 159.5 + 2.9 PLASMA CHLORIDE CONCENTRATION 114.9 + 3.2 113 .7 + 2.3 105.1 + 2.2 111. 0 + 2.7 113.8 + 2.9 103 . 6 + 1.7 107.6 106.2 + 2.3 + 4.2 116.9 + 3.9 115.3 + 1.5 103 . 9 + 2.8 106.0 + 2.9 121.0 + 2.0 122.3 + 2.9 105.9 + 2.8 111.01 + 2.0 106. 0 + 2.3 110.1 + 4.4 117.9 + 4.3 110. 3 + 3.4 109 . 8 + 2.8 102. 1 + 5.3 109.3 + 4.5 117.9 + 3.6 156.9 + 5.6 155. 0 + 6.1 150.2 + 2.0 158.5 + 3.2 112.9 + 5.5 118.3 + 8.8 107.4 + 6.0 106.8 + 3.2 122 . 5 + 4.4 450 168 . 3 + 12.5 194 . 5 + 18 . 0 159 .1 ± 6.0 156.7 + 8.7 120.4 + 11.7 145.7 + 21.3 110. 3 + 5.6 107.3 + 8.1 21 TABLE I I I . Continued. PLASMA OSMOLALITY Ducks females 299.4 287.1" 303.4 290.1** 291.5 291.6 (n=7) ± 7 . 3 +4.7 +7.2 +2.8 +8.0 +6.2 +19.8 males 296.7 286.8 301.0 291.4" 288.4 301.2 387.2" A (n=6) + 9.4 + 1.8 + 3.2 + 2.3 + 3.3 +10.3 +36.2 Geese females 292.8 287.5 294.0 303.9 294.6 303.0 315.5* (n=4) +7.8 ± 4 . 7 ± 6 . 0 ± 9 . 4 ±12.9 ±15.8 ±16.9 males 288.3 293.0 290.3 303.6* 291.4 293.2 309.8* (n=6) ± 6.6 ± 5.3 ± 6.4 ±12.2 ± 7.7 ± 5.4 ±17.9 G u l l s 3 (n=4) 294.5 314.8* 313.3 318.3 321.5 + 3.6 + 2.7 + 1.7 + 5.1 + 6.3 * ** P<0.01, P<0.005 Compared to values at the previous acclimation period, paired t - t e s t . P<0.05 Comparison of males and females, ANOVA. 3 G u l l s were acclimated to 112, 225, 340 and 375 mM NaCl. 22 Plasma AVT C o n c e n t r a t i o n : The [AVT] p l was the same i n ducks, geese and g u l l s d r i n k i n g f r e s h water (Table I) . As ducks were a c c l i m a t e d t o s a l i n e [AVT] p l g r a d u a l l y i n c r e a s e d , so t h a t when they drank 300 mM NaCl t h e i r [AVT] p l was s i g n i f i c a n t l y e l e v a t e d over f r e s h water v a l u e s (P<0.01, Ta b l e IV, F i g . 1). Compared t o f r e s h water v a l u e s , female and male geese [AVT] p l was i n c r e a s e d (P<0.01) when 225 mM NaCl was o f f e r e d (Table IV, F i g . 2 ) ; g u l l [AVT] p l tended t o i n c r e a s e (P<0.05) when 112 mM NaCl was g i v e n (Table IV, F i g . 3 ) . Plasma Ancf I I C o n c e n t r a t i o n : The [Ang H ] p l was the same i n ducks, geese and g u l l s d r i n k i n g f r e s h water (Table I ) . During the i n i t i a l stages of s a l i n e a c c l i m a t i o n duck [Ang H ] p l tended t o decrease, r e a c h i n g minimum v a l u e s i n both females and males d r i n k i n g 225 mM NaCl (P<0.05, T a b l e IV, F i g . 1) ; i t remained depressed u n t i l 450 mM NaCl was g i v e n , when i t i n c r e a s e d i n both sexes (P<0.01), alt h o u g h male duck [Ang H ] p l i n c r e a s e d more than female [Ang I I ] p l (P<0.05, Ta b l e I V ) . The [Ang I I ] p l of female and male geese remained unchanged u n t i l they drank 450 mM NaCl, when i t i n c r e a s e d i n females and males (P<0.01), such t h a t female geese had h i g h e r (P<0.05) [Ang H ] p l than male geese (Table IV, F i g . 2) . G u l l s i n i t i a l l y reduced [Ang H ] p l d u r i n g s a l i n e a c c l i m a t i o n , r e a c h i n g minimum l e v e l s (P<0.001) when b i r d s drank 225 mM NaCl, and r e t u r n e d t o f r e s h water l e v e l s when 375 23 TABLE IV. Mean plasma a n t i d i u r e t i c hormone (AVT) and angiotensin II (Ang II) concentration (pg/ml ± se) of female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s during s a l i n e acclimation. NaCl (mM) Ducks females (n=7) males (n=6) 48.4 ± 2.4 39.8 + 19.7 75 150 225 300 PLASMA AVT CONCENTRATION 375 106. 6 + 65.1 46.9 + 13.4 69.1 ±3 6.3 59.2 + 6.2 113.1 ±45. 0 83.9 +40.2 104 . 3 ±42 . 0 118.8+ + 10.8 156. ±25. 148 , + 30. 450 124.9 ±50.8 143 . 3 + 30.4 Geese females (n=4) males (n=6) 37. ±2 3 , 17, + 13, 47. ±39. 21, + 13 , 59.3 ±3 0.2 35.1 + 16.9 46.9* ±29.6 50.0* + 26.1 39, ±2 6. 41, + 29 , 4 9 , 1 .7 40, ±27 , 48, + 25, 1 3 6 0 53 . 0 ±45.0 65.8 +48.1 Gulls 0 1 (n=4) 35. 1 + 16.1 40, + 15, 43 . 8 + 6.8 54 , + 27 , 64 . 3 + 26.7 PLASMA ANG II CONCENTRATION Ducks females (n=7) males (n=6) 32. ±32. 51. + 32 , 33 . 0 ±23.3 30.9 + 13.7 8.7 ± 5.3 11.1 + 5.4 5.5 ± 3.5 7.0 + 3.2 10.4 + 11.9 12, + 10, 4 . ± 3. 7 , + 1. 61.1 ±2 0.0 244.0* + 37.4 Geese females (n=4) males (n=6) 27.5 ±10. 4 20.8 + 8.8 17.1 + 9.4 12 , + 9, 34.7 ±11. 3 32.5 + 11.2 21.8 ± 4.6 25.2 + 6.2 17, + 13, 19.4 + 7.8 38 . 8 ±12.5 28.2 + 3.5 121. 6 ±90.8 48.3*B + 27 . 9 Gulls'" (n=4) 59.6 + 12.5 44 , +20, 8.7* + 6.0 12 . 4 + 3.8 67 . 5 + 25.4 p<0.01, pai red +P<0.01 AP<0.05 B a, P<0.001 t - t e s t . Compared P<0.01 Compared to values at the previous acclimation to fresh water values. Comparison of males paired t - t e s t . and females, ANOVA. Gulls were acclimated to 112, 225, 540 and 375 mM NaCl. period. 24 mM NaCl was o f f e r e d (Table IV, F i g . 3). T o t a l Body Water; When b i r d s drank f r e s h water the TBW (% body mass) of g u l l s and ducks was s i m i l a r (P<0.5); g u l l TBW was h i g h e r (P<0.05) and duck TBW tended t o be h i g h e r (P<0.1) than t h a t of geese (Table V) . A f t e r a c c l i m a t i o n t o 300 mM NaCl, TBW was i n c r e a s e d (P<0.05) i n ducks and geese of both sexes, but was unchanged by a c c l i m a t i o n t o 375 mM NaCl i n g u l l s (Table V ) . 25 TABLE V. Total body water (% body mass ± se) of female and male Pekin ducks, female and male Canada geese and Glaucous-winged g u l l s during s a l i n e acclimation. TOTAL BODY WATER, % Body Mass NaCl Drunk (mM) 0 3 00 Ducks females 63.4 73.2 (n=7) ± 1 . 4 ± 5 . 2 males 65.3 74.4* (n=6) ± 7.6 ± 2.5 Geese females 53.1 64.7 (n=4) ± 3 . 2 ± 2 . 1 males 54.7 64.9* 2 (n=6) ± 3.6 ± 3.2 G u l l s 6 (n=4) 64.8 1 63.8 ± 1.4 ± 1.6 P<0.05 Compared to values at the fresh water regime, ANOVA. 1P<0.05 Compared to female and male geese, ANOVA. 2P<0.01 Compared to male ducks, ANOVA. ^Gulls were acclimated to 375 mM NaCl. 26 D I S C U S S I O N Pekin ducks, Canada geese and Glaucous-winged g u l l s d r i n k i n g f r e s h water had s i m i l a r Hct, plasma e l e c t r o l y t e c o n c e n t r a t i o n s , Osmpl, [AVT] p l, and [Ang H ] p l (Table I ) . The Hct, plasma i o n i c c o n c e n t r a t i o n s and Osmpl were w i t h i n ranges r e p o r t e d f o r these and o t h e r a v i a n s p e c i e s under s i m i l a r c o n d i t i o n s (Hughes and Ruch, 1969; Hughes, 1970a, 1980; Hammel, e t a l . , 1980; Roberts and Hughes, 1984). Body Mass: To some e x t e n t the d i f f e r e n c e s i n the observed changes i n body mass w i t h s a l t a c c l i m a t i o n i n ducks, geese and g u l l s (Table II) c o u l d have been due t o the time of y e a r i n which each s p e c i e s was s u b j e c t e d t o a c c l i m a t i o n . In g u l l s the experimental time was extended t o F a l l ; geese were a c c l i m a t e d d u r i n g S p r i n g time, and ducks were r e c r u i t e d d u r i n g Summer. The tendency t o reduce body mass i n ducks and geese d r i n k i n g 450 mM NaCl p r o b a b l y r e f l e c t s r e d u c t i o n of food i n t a k e (Holmes and P h i l l i p s , 1976) . My r e s u l t s support the i d e a t h a t Pekin ducks (Holmes, e t a l . , 1968, 1983), Canada geese (Hughes, Zenteno S a v i n and Kojwang, unpubl) and perhaps the Anatidae i n g e n e r a l , are unable t o m a i n t a i n body mass when a c c l i m a t e d t o sea water (Roberts and Hughes, 1984), w h i l e g u l l s i n c r e a s e d body mass a f t e r a c c l i m a t i o n t o 375 mM NaCl (Table I ) . 27 Hematocrit: Ducks tended t o i n c r e a s e Hct when d r i n k i n g 450 mM NaCl and geese showed a t r a n s i e n t i n c r e a s e when 150 mM NaCl was o f f e r e d (Table I I ) , i n d i c a t i n g changes i n f l u i d p a r t i t i o n i n g o r l o s s o f f l u i d from the i n t r a v a s c u l a r compartment (Hanwell, e t a l . , 1972; Crocker and Holmes, 1971; V a l e n t i n , e t a l . , 1989), and e x t r a c e l l u l a r d e h y d r a t i o n (Ramsay, e t a l . , 1977; Wood, e t a l . , 1980; R o l l s , e t a l . , 1980). In c o n t r a s t , d r i n k i n g c o n c e n t r a t e d s a l i n e d i d not a f f e c t Hct i n g u l l s (Table I I , Roberts and Hughes, 1984) which suggested t h a t plasma volume was b e i n g maintained. Plasma I o n i c C o n c e n t r a t i o n s and O s m o l a l i t y : Pekin ducks decreased [Na +] p l and Osmpl when they drank d i l u t e s a l i n e (Table I I I ) , and a t the same time, [Na +] i n the c l o a c a l f l u i d i n c r e a s e d (Hughes, Kojwang and Zenteno Savi n , i n p r e s s ) , s u g g e s t i n g Na + e x c r e t i o n i n u r i n e and f a e c e s may have exeeded Na + i n t a k e ; i n t r a c e l l u l a r f l u i d space may a l s o have become more r e a d i l y a v a i l a b l e t o Na + (Hughes and Ruch, 1969; Gray and Simon, 1983, 1985; Kaul and Simon, 1983; Roberts and Hughes, 1984; Gray, e t a l . , 1987). In g u l l s , s a l t a c c l i m a t i o n d i d not i n c r e a s e Na + space (Roberts and Hughes, 1984) , which i s c o n s i s t e n t w i t h the observed tendency towards i n c r e a s e d [Na +] p l i n g u l l s d r i n k i n g 340 mM NaCl (Table I I I ) . The Osmpl i n ducks and geese d r i n k i n g f r e s h water (Table I I I ) was w i t h i n the normal range f o r b i r d s (Hughes and Ruch, 28 1969; Hughes, 1970a, 1980; Hammel, e t a l . , 1980; Roberts and Hughes, 1984). The Osmpl of g u l l s d r i n k i n g f r e s h water (Table I I I ) was lower than p r e v i o u s l y observed i n t h i s s p e c i e s (Hughes, 1977), but c o a s t a l g u l l s do not u s u a l l y d r i n k f r e s h water and thes e b i r d s had been g i v e n f r e s h water f o r s e v e r a l months. When g u l l s drank 112 mM NaCl, Osmpl tended t o i n c r e a s e (Table I I I ) , which may have r e t u r n e d Osmpl t o normal v a l u e s , s i n c e i t d i d not i n c r e a s e w i t h f u r t h e r i n c r e a s e s i n d r i n k i n g water s a l i n i t y and g u l l Hct remained unchanged throughout the a c c l i m a t i o n p e r i o d ( F i g . 3) . The i n i t i a l i n c r e a s e i n g u l l Osmpl was not a s s o c i a t e d w i t h an i n c r e a s e i n [Na +] p l (Table I I I ) ; perhaps the presence o f oth e r o s m o t i c a l l y a c t i v e p a r t i c l e s a l l o w s the maintenance o f h i g h e r Osmpl i n these b i r d s as p a r t o f t h e i r a d a p t a t i o n t o marine environments. The Osmpl i n c r e a s e d i n ducks and geese d r i n k i n g 450 mM NaCl ( F i g s . 1, 2) i n d i c a t i n g they were dehydrated (Ramsay, e t a l . , 1977; Wood, e t a l . , 1980; R o l l s , e t a l . , 1980). When d r i n k i n g water s a l i n i t y was 340 mM NaCl o r g r e a t e r , duck Osmpl was c h r o n i c a l l y e l e v a t e d (Hammel, e t a l . , 1980), w h i l e g u l l s o n l y s l i g h t l y e l e v a t e d Osmpl under the same c o n d i t i o n s (Hughes, 1970a). The tendency t o i n c r e a s e [Na +] p l observed i n ducks and geese a t the l a s t stages o f s a l t a c c l i m a t i o n (Table I I I ) suggests d e h y d r a t i o n , s i n c e d e h y d r a t i o n i n c r e a s e d [Na +] p t i n g u l l s (Hughes and Lavery, 1974) and chic k e n s (Wideman, e t a l . , 1987) . Plasma AVT C o n c e n t r a t i o n : The i n i t i a l [AVT] p l of ducks, geese and g u l l s (Table IV) was h i g h e r than v a l u e s r e p o r t e d f o r b i r d s d r i n k i n g f r e s h water (Table V I ) . T h i s may be due t o the pre-sampling f a s t , s i n c e AVP r e l e a s e was s t i m u l a t e d by i n s u l i n and hypoglycemia i n man and dog (Zerbe, e t a l . , 1979). D i f f e r e n t RIA procedures c o u l d a l s o account f o r these d i f f e r e n c e s ; e x t r a c t i o n o f plasma w i t h Sep-Pak (as i n the p r e s e n t s t u d i e s ) y i e l d e d h i g h e r [AVT] p l than acetone e x t r a c t e d plasma (as used i n o t h e r s t u d i e s , Gray and Simon, 1983, 1985; Raveendran, 1987). D i f f e r e n c e s i n the g e n e t i c s t r a i n and age of experimental b i r d s c o u l d a f f e c t [AVT] p l; the s e n s i t i v i t y and osmotic t h r e s h o l d f o r AVP s e c r e t i o n are, a t l e a s t i n p a r t , g e n e t i c a l l y determined (Zerbe, 1985), and [AVP] p l i n c r e a s e d p r o g r e s s i v e l y w i t h age i n r a t s and humans ( F r o l k i s , e t a l . , 1982; Rondeau, e t a l . , 1982; K i r k l a n d , e t a l . , 1984; M i l l e r , 1985). The [AVT] p l o f Pekin ducks, Canada geese and Glaucous-winged g u l l s (Table IV) tended t o i n c r e a s e w i t h the c o n c e n t r a t i o n o f s a l t i n t h e i r d r i n k i n g water. The [AVT] p l i n c r e a s e d 3 t o 5 f o l d i n ducks when a c c l i m a t e d t o 340 mM NaCl (Gray and Simon, 1983, 1985), an increment s i m i l a r t o the observed (Table IV) . S u r p r i s i n g l y , [AVT] p l i n ducks d r i n k i n g 75 mM NaCl i n c r e a s e d (Table IV) as Osmpl decreased. An overcompensative water r e t e n t i o n , consequent t o e l e v a t e d [AVT] p l, might have been r e s p o n s i b l e f o r the i n i t i a l decrease i n duck Osm . ( F i g . 1). 30 FIGURE 1. The mean plasma a n t i d i u r e t i c hormone (AVT) and a n g i o t e n s i n I I (Ang II) c o n c e n t r a t i o n s , plasma o s m o l a l i t y , h e m a t o c r i t and body mass of male and female P e k i n ducks d u r i n g slow s a l i n e a c c l i m a t i o n . V e r t i c a l b a r s i n d i c a t e + one standard e r r o r . *P<0.01 Compared t o the p r e v i o u s a c c l i m a t i o n p e r i o d , p a i r e d t - t e s t . **P<0.01 Comparison of f r e s h water and 300 mM NaCl [AVT] . v a l u e s , p a i r e d t - t e s t . 31 Anas platyrynchos Female FIGURE 2. The mean plasma a n t i d i u r e t i c hormone (AVT) and a n g i o t e n s i n I I (Ang II) c o n c e n t r a t i o n s , plasma o s m o l a l i t y , h e m a t o c r i t and body mass o f male and female Canada geese d u r i n g slow s a l i n e a c c l i m a t i o n . V e r t i c a l b a r s i n d i c a t e + one stan d a r d e r r o r . *P<0.01 Compared t o t h e p r e v i o u s a c c l i m a t i o n p e r i o d , p a i r e d t - t e s t . **P<0.01 Comparison o f f r e s h water and 300 mM NaCl [AVT] . v a l u e s , p a i r e d t - t e s t . 33 Branto canadensis Mcle Femal AVT ( p g / m l ) ANG II ( p g / m l ) DRINKING WATER CONCENTRATION (mOsm/ l ) 34 FIGURE 3. The mean plasma a n t i d i u r e t i c hormone (AVT) and a n g i o t e n s i n I I (Ang II) c o n c e n t r a t i o n s , plasma o s m o l a l i t y , h e m a t o c r i t and body mass o f Glaucous-winged g u l l s d u r i n g slow s a l i n e a c c l i m a t i o n . V e r t i c a l b a r s i n d i c a t e + one st a n d a r d e r r o r . *P<0.01 Compared t o the p r e v i o u s a c c l i m a t i o n p e r i o d , p a i r e d t - t e s t . 35 LOTUS g l a u c e s c e n s OSMOLALITY (mOsm/l) HEMATOCRIT m (%) BODY MASS J"1 (g) : DRINKING WATER CONCENTRATION (mOsm / l ) 36 TABLE VI. Plasma a n t i d i u r e t i c hormone concentration i n mammals (arginine vasopressin, AVP, appendix F i g . 1) and birds (arginine vasotocin, AVT, appendix Fig 1.) drinking fresh water. Species pg/ml se n Reference MAMMALS Dog1 3.1 + 0. 8 - Goetz and Wang, 1985 Human2 1.4 + - 10 Vokes and Robertson, 1985 Rat 3 1.5 + 2 . 8 7 Morris, et a l , 1984 10.4 + 2 . 5 8 Yamaguchi, et a l , 1982 Rabbit 4 9.4 + 3 . 2 7 King, et a l , 1989 BIRDS Fowl 5 4.4 + 0. 9 - Koike, et a l , 1977 9.6 + 1. 6 6 Rice, et a l , 1985 12 . 6 + 1. 0 8 Stallone and Braun, 1986 Pekin Duck6 5.1 + 1. 5 7 Mohring, et a l , 1980 5.8 + 3 . 0 18 Gray, 1987 4.2 + 1. 1 16 Simon and Gray, 1989 Japanese Q u a i l 7 10.0 - - Kobayashi and Takei, 1982 Kelp G u l l 8 15. 0 + 1. 1 20 Gray, 1987 13 . 6 + 1. 1 10 Gray and Erasmus, 1989 Cape Gannet 9 4 . 6 + 0. 4 8 Gray, 1987 Jackass Penguin 1 0!!. 1 + 1. 1 8 Gray, 1987 Os t r i c h 1 1 10.2 + 1. 3 10 Gray, 1987 Canis f a m i l i a r i s ; Homo sapiens; Rattus spp; Oryctolagus cuniculus; ^ C a l l u s domesticus; 6Anas ptatyrhynchos; ^Coturnix japonica; ^Larus dominicanus; 'sula capensis; 1"spheniscus demersus; ^Struthio camelus. 37 I n c r e a s e d [AVT] p l without simultaneous i n c r e a s e i n Osmpl i n the t h r e e s p e c i e s s t u d i e d ( F i g s . 1, 2, 3) does not agree w i t h the p r e v i o u s l y observed p o s i t i v e c o r r e l a t i o n between Osmpl and [AVT] p l (Hammel, e t a l . , 1980; Mohring, e t a l . , 1980; Gray and Simon, 1983; Skadhauge, e t a l . , 1983; Ge r s t b e r g e r , e t a l . , 1985; Raveendran, 1987; Simon-Oppermann, e t a l . , 1988; Brummermann and Simon, 1990). On the o t h e r hand, n e i t h e r Gray and Erasmus (1988) nor Wang, e t a l . , (1989) found a c o r r e l a t i o n between Osmpl and [AVT] p l i n the Kelp g u l l (L dominicanus) o r fowl, r e s p e c t i v e l y . P r e v i o u s s t u d i e s r e p o r t e d changes i n [AVT] p l i n response t o in t r a v e n o u s ( i v ) NaCl i n f u s i o n o r compared b i r d s a c c l i m a t e d t o f r e s h water w i t h b i r d s kept f o r l o n g p e r i o d s on s a l i n e . Slow a c c l i m a t i o n should have t r i g g e r e d homeostatic mechanisms which would m a i n t a i n Osmpl and plasma e l e c t r o l y t e c o n c e n t r a t i o n s w i t h i n the normal p h y s i o l o g i c a l range (Skadhauge, 1969; Braun and D a n t z l e r , 1972, 1974, 1984; Bentley, 1976; S t a l l o n e and Braun, 1985). I n f u s e d AVT decreased Osmpl i n fowl ( S t a l l o n e and Braun, 1985), and e l e v a t e d [AVT] p l was a s s o c i a t e d w i t h reduced [Na +] p l i n the goose Anser anser (Peaker, 1971) ; thus, the observed maintenance o f Osmpt and [Na +] p l i n b i r d s d u r i n g s a l t a c c l i m a t i o n c o u l d w e l l be the r e s u l t o f the p r o g r e s s i v e i n c r e a s e s i n [AVT] p l. The osmotic t h r e s h o l d f o r AVP r e l e a s e was g r e a t e r when i t was o b t a i n e d by s a l i n e i n f u s i o n ( i n c r e a s e d ECFV) than by water d e p r i v a t i o n (decreased ECFV), and p r o g r e s s i v e decreases i n 38 b l o o d volume produced p r o g r e s s i v e i n c r e a s e s i n the s l o p e o f the r e g r e s s i o n l i n e r e l a t i n g AVP t o Osmpl (Robertson, 1985). A c c o r d i n g l y , osmotic t h r e s h o l d f o r AVT r e l e a s e i n Pekin ducks and Canada geese i n c r e a s e d when they drank 300 mM NaCl, but decreased when 450 mM NaCl was pres e n t e d (Table V I I ) , su g g e s t i n g ECFV expansion and de h y d r a t i o n , r e s p e c t i v e l y . Glaucous-winged g u l l s appeared t o m a i n t a i n ECFV, s i n c e osmotic t h r e s h o l d and s e n s i t i v i t y were unchanged a f t e r a c c l i m a t i o n t o 375 mM NaCl (Table V I I ) . Plasma Ang I I C o n c e n t r a t i o n : The [Ang H ] p l i n b i r d s d r i n k i n g f r e s h water (Table IV) was w i t h i n the r e p o r t e d range f o r b i r d s and mammals (Table V I I I ) . A l l t h r e e s p e c i e s decreased [Ang I I ] p l d u r i n g a c c l i m a t i o n t o moderately c o n c e n t r a t e d s a l i n e (Table IV) i n c o n t r a s t w i t h p r e v i o u s s t u d i e s (Gray and Simon, 1984; Brummermann and Simon, 1990). Fowl decreased plasma r e n i n a c t i v i t y (PRA) f o l l o w i n g h y p e r t o n i c NaCl i n f u s i o n (Nishimura and B a i l e y , 1982), which i s c o n s i s t e n t w i t h the observed i n i t i a l decrease i n [Ang H ] p t (Table I V ) . Increased PRA was a s s o c i a t e d w i t h the long-term a d m i n i s t r a t i o n o f the d i u r e t i c xipamide i n man ( L i j n e n , e t a l . , 1989), s u g g e s t i n g t h a t the change i n plasma r e n i n may be r e l a t e d t o d i u r e t i c - i n d u c e d volume c o n t r a c t i o n . Conversely, the volume expansion t h a t would r e s u l t from i n c r e a s e d [AVT] p l i n s a l i n e a c c l i m a t e d b i r d s (Table IV) c o u l d decrease PRA and, presumably, [Ang I I ] D , . Hypotension s t i m u l a t e d AVP s e c r e t i o n TABLE V I I . R e l a t i o n s h i p o f plasma a r g i n i n e v a s o t o c i n ([AVT] p l) t o plasma o s m o l a l i t y (Osm t) i n female and male P e k i n ducks, female and male Canada geese and Glaucous-winged g u l l s d u r i n g s a l i n e a c c l i m a t i o n . Ducks females (n=7) 0 mM NaCl 300 mM NaCl 450 mM NaCl males (n=6) 0 mM NaCl 300 mM NaCl 450 mM NaCl Geese females (n=4) 0 mM NaCl 300 mM NaCl 450 mM NaCl males (n=6) [AVT] [AVT] t [AVT] t [AVT] t [AVT] t [AVT] = 0. 62 * [Osm = 1. 45 * [Osmj 2. 39 * [Osm( 0. 43 * [Osm = 1. 84 * [Osmj •= 2. 57 * [Osm p l p i l p l 253.56], 335.57], 247.52], 275.01], 334.45], 240.80], r r r r r r 0.66 0.46 0.60 0.88 0.88 0.57 [AVT] = [AVT] = [AVT] = 0. 69 * [°sm p l [Osmpl [Osmpl - 268 .54] , r = 0. 74 1. 55 * - 284 • 43] , r = 0. 60 1. 59 * - 238 .10] , r = 0. 23 0 mM NaCl [AVT] [AVT] t [AVT] { = 0. 59 * [Osmpl [Osmpl [Osmpt - 276. 24] , r = 0. 73 300 mM NaCl = 0. 92 * - 336. 70] , r = 0. 24 450 mM NaCl = 1. 50 * - 240. 17], r = 0. 22 G u l l s (n=4) 0 mM NaCl 375 mM NaCl [AVT] t = 2.46 * [Osm t - 300.30], r = 0.99 [AVT] p l = 2.65 * [Osmpl - 294.99], r = 0.64 LAvnpl = b c o e f f i c i e n t 'pl m/b ] ; where m i s the y - i n t e r c e p t , the r e g r e s s i o n o r s l o p e (b ) p r o v i d e s measure o f the s e n s i t i v i t y , and the x -i n t e r c e p t (m/b) of t he l i n e p r o v i d e s measure o f the s e t p o i n t o r t h r e s h o l d . The c o r r e l a t i o n c o e f f i c i e n t ( r ) i n d i c a t e s t he p r e c i s i o n o f t he osmoregu la to r y mechanism. 40 TABLE VIII. Plasma angiotensin II concentration i n mammals and birds (appendix Fig 2.) drinking fresh water. Species pg/ml se n Reference MAMMALS Dog1 70.1 ± 11. 2 19 Nichols, 1979 14.2 ± 1. 6 4 Reid, et a l , 1982 Human2 12 .0 ± 2. 1 11 Shimamoto, et a l , 1984 Rat 3 29.3 ± 3 . 5 10 Yamaguchi, et a l , 1982 C a l f 4 57.2 ± 1. 1 6 B e l l and Doris, 1983 Rabbit 5 18.5 ± 4 . 0 6 Schuster, et a l , 1984 BIRDS Pekin Duck6 16. 4 ± 0. 7 Simon--Oppermann, et a l , 1984 35.3 ± 3 . 9 22 Gray and Simon, 1985 67 . 7 ± 28. 7 - Gray and Simon, 1987 Japanese Q u a i l 7 29.7 - - Okawara, et a l , 1986 61.3 ± 9 . 9 6 Takei, et a l , 1988 Kelp G u l l 8 58.1 ± 5. 4 20 Gray, 1987 53.5 ± 12. 7 - Gray and Erasmus, 1988 48.1 ± 5. 4 10 Gray and Erasmus, 1989 Cape Gannet 9 167.7 + 18. 6 8 Gray, 1987 Jackass Penguin 1 0 107 .1 ± 21. 6 8 Gray, 1987 Ost r i c h 1 1 44 . 3 ± 2. 5 10 Gray, 1987 Canis familiaris; Homo sapiens; Rattus spp; Bovus sp; Oryctolagus cuniculus; 6Anas platyrhynchos; 7Coturnix japonica; 8Larus dotninicanus; Sula capensis; 1 0Spheniscus demersus; Struthio camelus. 41 i n mammals (Robertson, 1985; Cowley, e t a l . , 1985). The hypotension r e s u l t i n g from decreased [Ang I I ] p l (Nishimura, e t a l . , 1984) i n b i r d s a c c l i m a t e d t o d i l u t e s a l i n e (Table IV) might have s t i m u l a t e d the observed i n c r e a s e s i n [AVT] p l (Erbe, e t a l . , 1985; Goto, e t a l . , 1986; Koike, 1989) without a f f e c t i n g Osmpl ( F i g s . 1, 2, 3), thus the osmotic r e l e a s e o f AVT i n b i r d s w i t h s a l t glands may be o v e r r i d e n by oth e r s t i m u l i , such as decreased b l o o d p r e s s u r e (Nishimura, e t a l . , 1984) . Decreases i n [Ang I I ] p l c o u l d induce both l o c a l and i n d i r e c t a c t i o n s t o decrease d i u r e s i s through d i m i n i s h e d plasma l e v e l s of a l d o s t e r o n e (Wilson, e t a l . , 1985; Erbe, e t a l . , 1985, 1988; Gray and Simon, 1984, 1985) and catecholamines (Nishimura, e t a l . , 1982; Wilson and B u t l e r , 1983a, b; Wilson and West, 1986). Decreased [Ang I I ] p l p a i r e d t o i n c r e a s e d [AVT] p l can be expected t o decrease GFR i n ducks ( a f t e r Gray, e t a l . , 1986; Raveendran, 1987; Gray and Erasmus, 1989), which, i n t u r n , would decrease the r a t e o f r e n a l l o s s o f water. T h e r e f o r e , decreased [Ang H ] p l and i n c r e a s e d [AVT] p l would promote water r e t e n t i o n . T h i s c o u l d account f o r the decreased [Na +] p l and Osmpl i n ducks d r i n k i n g 75 mM NaCl ( F i g . 1) • Increase d Hct (Table II) , [Na +] p t and Osmpl (Table I I I , F i g s . 1, 2) a l l i n d i c a t e d e h y d r a t i o n (Shade and Share, 1975; Robertson and Athar, 1976; Hayward e t a l . , 1976; Gray and Simon, 1983; 1987; Gray and Erasmus, 1988). Decreased ECF and 42 v a s c u l a r volume, due t o d e h y d r a t i o n d u r i n g the l a s t stages of s a l t a c c l i m a t i o n , c o u l d have s t i m u l a t e d r e l e a s e of Ang I I g i v i n g r i s e t o the e l e v a t e d [Ang H ] p l observed i n ducks and geese ( F i g s . 1, 2) . In accordance t o the macula densa th e o r y of r e n i n r e l e a s e (Davis and Freeman, 1976; Reid, 1984; Nishimura, e t a l . , 1984), d i m i n i s h e d e f f e c t i v e r e n a l plasma flow r e s u l t i n g from i n c r e a s e d [AVT] p t when b i r d s drank 450 mM NaCl (Table IV, Raveendran, 1987) c o u l d have s t i m u l a t e d r e n i n r e l e a s e and generated Ang I I i n plasma. C h r o n i c a l l y s a l t s t r e s s e d , dehydrated ducks d i d not show changes i n b l o o d volume, but s i g n i f i c a n t l y reduced t h e i r t o t a l ECFV and e l e v a t e d t h e i r [Ang H ] p l (Brummermann, 1988) . The [Ang I I ] p l i n b i r d s i n c r e a s e s w i t h s t r e s s (Gray, pers comm) . The i n c r e a s e s i n [Ang H ] p l observed i n ducks and, t o a l e s s e r e x t e n t , geese d r i n k i n g 450 mM NaCl (Table IV) o b v i o u s l y r e f l e c t the s t r e s s f u l s i t u a t i o n produced by water and e l e c t r o c h e m i c a l imbalances due t o severe d e h y d r a t i o n . Except i n ducks and geese d r i n k i n g 450 mM NaCl ( F i g s . 1, 2) , n e i t h e r the i n v e r s e r e l a t i o n s h i p between [Ang I I ] p l and ECFV (assuming i n c r e a s e d Hct i n d i c a t e d decreased ECFV, Gray and Simon, 1985; Simon-Oppermann, e t a l . , 1988; Brummermann and Simon, 1990), nor the p o s i t i v e c o r r e l a t i o n between [Ang I I ] p l and Osmpl (Gray and Simon, 1984, 1985) were observed ( F i g . 1) . These i n c o n s i s t e n c i e s may r e f l e c t d i f f e r e n c e s i n the experimental p r o t o c o l s . Other r e s e a r c h e r s (Gray and Simon, 1985; Simon-Oppermann, e t a l . , 1988; Brummermann and Simon, 43 1990) u s u a l l y imposed s a l i n e s o l u t i o n s a c u t e l y ; i n the p r e s e n t study the animals were allowed t o i n g e s t s a l i n e a t w i l l . E l e v a t e d [Ang H ] p l i n h i b i t s SGS (Hammel and Maggert, 1983; Ge r s t b e r g e r , e t a l . , 1984; Wilson, e t a l . , 1985; Gray and Simon, 1985) ; c o n v e r s e l y , low l e v e l s o f [Ang H ] p l should a l l o w SGS t o occur. E x t r a r e n a l NaCl s e c r e t i o n t o g e t h e r w i t h water r e t e n t i o n ( i n c r e a s e d AVT) would m a i n t a i n Osmpl and Hct (and presumably ECFV), as observed when b i r d s drank low t o moderately c o n c e n t r a t e d s a l i n e ( F i g s . 1, 2, 3). When b i r d s were g i v e n 450 mM NaCl, t h e i r l i m i t e d c a p a c i t y t o e x c r e t e Na* r e n a l l y and the i n h i b i t i o n o f SGS caused by h i g h [Ang I I ] p l (Gray and Simon, 1985) were r e f l e c t e d as i n c r e a s e d Hct and Osmpl i n ducks ( F i g . 1) , and an i n c r e a s e i n Osmpl without s i g n i f i c a n t i n c r e a s e i n Hct i n geese ( F i g . 2 ) . T h i s supports t h e i d e a t h a t s a l t r e t e n t i o n h e l p s t o m a i n t a i n ECFV a t the expense o f sometimes e x c e s s i v e r i s e s i n ECF t o n i c i t y (Simon, e t a l . , 1989; Ger s t b e r g e r , e t a l . , 1989). The [Ang I I ] t decreased d u r i n g the f i r s t s tages o f s a l i n e a c c l i m a t i o n i n Glaucous-winged g u l l s (Table IV) . Yet, a f t e r an i n i t i a l tendency t o i n c r e a s e ( F i g . 3) , Osmpl and plasma e l e c t r o l y t e c o n c e n t r a t i o n s remained unchanged, which might i n d i c a t e t h a t g u l l s had a h i g h e r s e n s i t i v i t y t o Ang I I than e i t h e r ducks o r geese. S a l t a c c l i m a t i o n decreased the Ang I I t h r e s h o l d c o n c e n t r a t i o n r e q u i r e d f o r i n v i t r o neuronal e x c i t a t i o n i n ducks (Simon, e t a l . , 1989), and induced an ad a p t i v e u p r e g u l a t i o n o f Ang I I r e c e p t o r d e n s i t y i n the 44 s u b f o r n i c a l organ (Gerstberger, e t a l . , 1987a, b) . T h i s suggested t h a t h i g h s a l t i n t a k e heightens the re s p o n s i v e n e s s t o Ang I I . The r e s u l t s from t h i s study might i n d i c a t e t h a t the enhanced s e n s i t i v i t y t o Ang I I found i n s a l t a c c l i m a t e d ducks i s n a t u r a l l y e x h i b i t e d i n the more marine s p e c i e s , the Glaucous-winged g u l l . In mammals, a t r i a l n a t r i u r e t i c f a c t o r (ANF) and Ang I I have opposing a c t i o n s (Mannix, e t a l . , 1990). Under acute Na* excess, mammals i n c r e a s e d ANF t o reduce c a r d i a c p r e l o a d v i a m u l t i p l e mechanisms, i n c l u d i n g RAS s u p p r e s s i o n , and under c h r o n i c r e n a l h y p o p e r f u s i o n , they i n c r e a s e d RAS t o m a i n t a i n an e f f e c t i v e i n t r a v a s c u l a r volume (Carlone, e t a l . , 1989). The b i p h a s i c response of [Ang H ] p l of ducks, geese and g u l l s d u r i n g s a l t a c c l i m a t i o n (Table IV) appears t o support the proposed p r e f e r e n t i a l r o l e o f the RAS i n m a i n t a i n i n g i n t r a v a s c u l a r volume d u r i n g c h r o n i c i n c r e a s e i n i n g e s t e d Na +. However, when Pekin ducks and Canada geese (Table IV) drank 450 mM NaCl the i n c r e a s e d [Ang I I ] p l resembled [Ang H ] p l i n dehydrated b i r d s (Gray and Simon, 1987, 1988). When g u l l s drank 375 mM NaCl [Ang I I ] p l r e t u r n e d t o f r e s h water v a l u e s , and [AVT] p l had i n c r e a s e d l e s s than i n Pekin ducks and Canada geese (Table I V ) . T h i s would have favoured a h i g h e r GFR i n g u l l s than i n ducks and geese, as had been r e p o r t e d p r e v i o u s l y (Hughes, 1980). At the same time, [Ang I I ] p l i n g u l l s d i d not reach l e v e l s which would have s i g n i f i c a n t l y i n h i b i t e d SGS (Table IV, Gray, e t a l . , 1986; Gray, 1987; Ger s t b e r g e r , e t a l . , 1987a, b ) . The o v e r a l l r e s u l t would be a simultaneous, c o n c e r t e d f u n c t i o n o f kidneys and s a l t glands i n g u l l s , r a t h e r than SGS i n the absence o f r e n a l f i l t r a t i o n seen i n ducks (Simon-Oppermann, e t a l . , 1984). The Hct, Osmpl and [AVT] p l i n c r e a s e d when ducks drank 450 mM NaCl ( F i g . 1), i n d i c a t i n g d e h y d r a t i o n . T h i s i s i n c o n t r a s t t o the a l r e a d y h i g h plasma e l e c t r o l y t e c o n c e n t r a t i o n (Table I I I ) . While the i n c r e a s e d [AVT] p l would a i d i n f l u i d r e t e n t i o n , duck kidneys (Simon, 1982) and s a l t glands (Holmes, e t a l . , 1961; Hughes and Ruch, 1969; Hughes, e t a l . , 1991) have a l i m i t e d a b i l i t y t o c o n c e n t r a t e Na +. Pekin ducks [Ang I I ] t i n c r e a s e d (Table IV, F i g . 1) a t the h i g h e s t d r i n k i n g water s a l i n i t y . E l e v a t e d [Ang H ] p l may i n c r e a s e d r i n k i n g ( T a k e i , e t a l . , 1985, 1989), but decrease s e c r e t i o n r a t e (Gray and Simon, 1985). Thus, i n c r e a s e d i n g e s t i o n o f moderately c o n c e n t r a t e d s a l i n e would produce f r e e water f o r maintenance o f plasma c o n c e n t r a t i o n but v e r y c o n c e n t r a t e d s a l i n e would i n c r e a s e plasma e l e c t r o l y t e c o n c e n t r a t i o n s and Osmpl, as was observed (Table I I I ) . I f Ang I I s t i m u l a t e s d i u r e s i s (Thomas and Skadhauge, 1985; Wilson, e t a l . , 1985; Gray and Simon, 1985) and n a t r i u r e s i s (Gray and Simon, 1983; S t a l l o n e and Nishimura, 1985), ducks and geese d r i n k i n g sea water would f i n d themselves i n a c u l -de-sac; s i n c e e x c e s s i v e f l u i d l o s s would f u r t h e r i n c r e a s e volume d e p l e t i o n and plasma c o n c e n t r a t i o n , l e a d i n g t o the r e l e a s e o f y e t more AVT and Ang I I . Plasma AVT and Ang I I C o n c e n t r a t i o n s i n Male and Female Ducks  and Geese: Female domestic fowl, G a l l u s domesticus. Japanese q u a i l , C o t u r n i x c o t u r n i x i a p o n i c a . and pigeon, Columba l i v i a , had lower [AVT] p l than males (Niezgoda and Rzasa, 1971; Niezgoda, 1975). F o l l o w i n g haemorrhage and d e h y d r a t i o n , hens i n c r e a s e d [AVT] p l l e s s than cocks (Niezgoda, 1975; 1978). In c o n t r a s t , no s i g n i f i c a n t c o r r e l a t i o n between sex and [AVT] p l was found (Table IV) , although female Pekin ducks and Canada geese d r i n k i n g " f r e s h water tended t o have h i g h e r [AVT] p l than males, and i n c r e a s e d i t l e s s over the a c c l i m a t i o n p e r i o d than males d i d . While most female Pekin ducks a c c l i m a t e d t o 450 mM NaCl v o i d e d l a r g e c l o a c a l f l u i d samples, males f a i l e d t o produce c l o a c a l f l u i d o r produced s e m i - s o l i d p e l l e t s (Hughes, Kojwang and Zenteno Sav i n , i n p r e s s ) . The r e l a t i v e l y s m a l l e r i n c r e a s e i n [AVT] p l i n female ducks (Table IV) supports these o b s e r v a t i o n s . Female ducks i n c r e a s e d [Ang H ] p i (P<0.05) and Osmpl (P<0.05) l e s s than males d u r i n g exposure t o 450 mM NaCl ( F i g . 1) ; w h i l e female geese i n c r e a s e d [Ang H ] p l (P<0.05) more than males ( F i g . 2) . In mammals, plasma r e n i n s u b s t r a t e c o n c e n t r a t i o n i n c r e a s e d a f t e r treatment w i t h e s t r o g e n (Fernandez, e t a l . , 1985; Cabrera, e t a l . , 1986; Sealey, e t a l . , 1986, 1987; de V i t o , e t a l . , 1987), and progesterone i n c r e a s e d plasma r e n i n l e v e l s (de V i t b , e t a l . , 1989). Female Pekin ducks a c c l i m a t e d t o 450 mM NaCl tended t o have 47 l a r g e r kidneys than males and, although s a l t g l a n d s i z e was the same, females appeared t o produce l e s s SGS (Hughes, Kojwang and Zenteno Savi n , unpubl), which seems t o be i n c o n t r a s t t o the s m a l l e r i n c r e a s e i n [Ang I I ] p l i n female ducks (Table I V ) , g i v e n the i n h i b i t o r y e f f e c t on SGS a t t r i b u t e d t o t h i s hormone (Hammel and Maggert, 1983; B u t l e r , e t a l . , 1989; G e r s t b e r g e r , e t a l . , 1989). However, the d e h y d r a t i o n suggested by the decreased body mass, and i n c r e a s e d Hct, plasma e l e c t r o l y t e c o n c e n t r a t i o n s and Osmpl i n ducks ( F i g . 1), when 450 mM NaCl was o f f e r e d , may have s t i m u l a t e d SGS (Stewart, 1972), w h i l e [Ang I I ] p l may have i n c r e a s e d i n response t o the decreased ECFV. T o t a l Body Water; The TBW (% body mass) of ducks, geese and g u l l s d r i n k i n g f r e s h water (Table V) was w i t h i n the normal range f o r b i r d s (Thomas and P h i l l i p s , 1975; Hughes, 1983; T a k e i , e t a l . , 1989) . W i l d M a l l a r d females had a h i g h e r TBW than males (Hughes, 1983) ; however, no d i f f e r e n c e s i n TBW were found between females and males i n e i t h e r Pekin ducks or Canada geese (Table V ) . In c o n t r a s t t o t h i s study (Table V) , a c c l i m a t i o n t o s a l t water d i d not change TBW of M a l l a r d s (Hughes, 1983) . Change i n TBW w i t h s a l i n e a c c l i m a t i o n among b i r d s w i t h s a l t glands c o u l d r e f l e c t the a b i l i t y o f the s a l t glands t o produce f r e e water. I f d r i n k i n g water i s f r e e l y a v a i l a b l e , s p e c i e s l i k e the 48 Glaucous-winged g u l l t h a t are w e l l adapted t o f l u c t u a t i o n s i n environmental s a l t c o n c e n t r a t i o n should m a i n t a i n a co n s t a n t TBW d e s p i t e changes i n s a l i n i t y o f t h e i r d r i n k i n g water or food (Walter and Hughes, 1978) , as was confirmed (Table V ) . G u l l s a r e c a r n i v o r o u s , they can o b t a i n s u b s t a n t i a l amounts of water from t h e i r food (Takei, e t a l . , 1989) and, as marine b i r d s , t h e i r k idneys c o n t a i n more MT nephrons than o t h e r b i r d s (Braun, 1984), a l l o w i n g them t o c o n c e n t r a t e u r i n e ; a l s o , they can e x t r a c t more f r e e water i n the p r o d u c t i o n of SGS than ducks (Hughes, 1970b; Skadhauge, 1975; Braun and D a n t z l e r , 1984; Hughes, e t a l . , 1987). Some o f the i n c r e a s e i n TBW i n ducks and geese may r e s u l t from replacement of body f a t w i t h water. Osmotic t h r e s h o l d f o r AVT r e l e a s e was h i g h e r i n Pekin ducks and Canada geese of both sexes a f t e r a c c l i m a t i o n t o 300 mM NaCl (Table V I I ) , s u g g e s t i n g ECFV expansion (Robertson, 1985). An i n c r e a s e i n ECFV i n p r o p o r t i o n t o TBW i s c o n s i s t e n t w i t h the observed decrease i n [Ang I I ] p l when b i r d s were d r i n k i n g low t o moderately c o n c e n t r a t e d s a l i n e (Table IV) ; SGS would have been s t i m u l a t e d more e a s i l y as a r e s u l t o f ECFV expansion (Ruch and Hughes, 1975; Zucker, e t a l . , 1977; Hammel, e t a l . , 1980; Hughes, 1989a, b ) . A c c l i m a t i o n t o 300 mM NaCl i n c r e a s e d mean d a i l y water f l u x (MDWF) i n ducks by 70 % (Hughes, e t a l . , 1991) and i n geese by 100 % (Hughes, Zenteno S a v i n and Kojwang, unpubl) but not g u l l MDWF (375 mM NaCl, p r e s e n t study, or f u l l s t r e n g t h sea water, Walter and Hughes, 1978). When 300 mM NaCl was o f f e r e d , duck 49 and geese [Ang H ] p l was approximately 70 % and 20 % lower, r e s p e c t i v e l y , than when they drank f r e s h water ( F i g s . 1, 2), w h i l e g u l l [Ang I I ] p l had r e t u r n e d t o f r e s h water v a l u e s ( F i g . 3) . S i n c e water f l u x i n c r e a s e d as [Ang H ] p l decreased when ducks were g i v e n 300 mM NaCl (Zenteno S a v i n and Huges, unpubl), o t h e r s t i m u l i , such as c e l l u l a r and e x t r a c e l l u l a r d e h y d r a t i o n ( T a k e i , e t a l . , 1989) or [AVT] p l (Robertson, 1985) may r e g u l a t e d r i n k i n g i n b i r d s w i t h s a l t g l a n d s . E v i d e n t l y , ducks and geese i n c r e a s e d MDWF i n o r d e r t o d e r i v e water by s a l t g l a n d s e c r e t i o n . Duck SGS had roughl y the same [Na +] p t as t h e i r d r i n k i n g water (Hughes, e t a l . , 1991), w h i l e goose (Hughes, Zenteno S a v i n and Kojwang, unpubl) and g u l l (Hughes, 1970a, 1970b) SGS was two t o t h r e e times more c o n c e n t r a t e d than t h e i r d r i n k i n g water. Thus, ducks would e x t r a c t much l e s s f r e e water from the same s a l i n e s o l u t i o n than geese and g u l l s , (Hughes, 1970a), as suggested by the i n c r e a s e d Hct i n ducks d r i n k i n g 450 mM NaCl ( F i g . 1) and the maintenance o f Hct i n geese and g u l l s ( F i g s . 2, 3). As i n d i c a t e d by the maintenance of body mass, Hct, plasma e l e c t r o l y t e c o n c e n t r a t i o n and Osmpl ( F i g s . 1, 2, 3), f o l l o w i n g a c c l i m a t i o n t o 300 mM NaCl, Pekin ducks and Canada geese maintained hydrosmotic balance by i n c r e a s i n g TBW and [AVT] p l, and d e c r e a s i n g [Ang H ] p l , which would favour SGS (Gray and Simon, 1985). Apparently, ducks achieved hydrosmotic balance by i n i t i a l l y i n c r e a s i n g c l o a c a l i o n e x c r e t i o n and p r o b a b l y r e d i s t r i b u t i n g Na + from the i n t r a v a s c u l a r t o the i n t r a c e l l u l a r 50 compartment, without a s i g n i f i c a n t change i n Hct (Table I I ) , and Canada geese, by an i n i t i a l i n c r e a s e i n Hct (Table I) and i n c r e a s e d SGS c o n c e n t r a t i o n , which suggests m i l d e x t r a c e l l u l a r d e h y d r a t i o n . Glaucous-winged g u l l s , produced c o n c e n t r a t e d SGS r e g a r d l e s s o f d r i n k i n g water s a l i n i t y (Hughes, 1970a). T h i s was an e f f e c t i v e mechanism f o r g u l l s t o m a i n t a i n osmotic balance, s i n c e n e i t h e r TBW (Table V) nor MDWF (Walter and Hughes, 1978) were i n c r e a s e d by s a l i n e a c c l i m a t i o n . The Hct, plasma e l e c t r o l y t e c o n c e n t r a t i o n s and Osmpl i n c r e a s e d i n ducks and geese d r i n k i n g 450 mM NaCl, i n d i c a t i n g d e h y d r a t i o n , a s t i m u l a n t f o r s e c r e t i o n o f AVT (Shade and Share, 1975; Robertson and Athar, 1976; Hayward, e t a l . , 1976; Gray and Simon, 1983, 1987; Gray and Erasmus, 1988) and Ang I I (Koike, e t a l . , 1977; Nouwen e t a l . , 1984; Gray, 1987). Dehydration may a l s o s t i m u l a t e SGS (Stewart, 1972). G u l l s were not a c c l i m a t e d t o 450 mM NaCl but a t t h i s c o n c e n t r a t i o n they m a i n t a i n body mass, Hct, and [Na +] p l, w h i l e [ C l " ] p l and Osmpl are s l i g h t l y e l e v a t e d (Hughes, 1977) . The observed r e l a t i v e constancy i n body mass, Hct and Osmpl ( F i g . 3) i s i n accordance w i t h expected responses o f g u l l s d r i n k i n g h i g h l y c o n c e n t r a t e d s a l i n e . 51 C O N C L U S I O N S Peki n ducks, Canada geese and Glaucous-winged g u l l s responded d i f f e r e n t l y t o slow s a l i n e a c c l i m a t i o n . As hyp o t h e s i z e d , plasma i o n i c c o n c e n t r a t i o n s and Hct (and presumably ECFV) remained unchanged, as lo n g as b i r d s e x c r e t e d excess s a l t without l o s i n g body water. Ducks and geese maintained body mass, Hct, plasma e l e c t r o l y t e c o n c e n t r a t i o n s and Osmpl by i n c r e a s i n g TBW, MDWF and [AVT] p l, they a l s o decreased [Ang I I ] p l , which would favour SGS. Ducks achieved h y d r o s t a t i c balance by i n i t i a l l y e l e v a t i n g c l o a c a l i o n e x c r e t i o n and p o s s i b l y by r e d i s t r i b u t i n g Na + from the i n t r a v a s c u l a r t o the i n t r a c e l l u l a r compartment, without a s i g n i f i c a n t change i n Hct or c o n c e n t r a t i o n o f the s a l t g l a n d s e c r e t i o n ; geese i n i t i a l l y i n c r e a s e d Hct, which suggests m i l d d e h y d r a t i o n ; and g u l l s i n i t i a l l y i n c r e a s e d Osmpl, but t h i s p r o b a b l y was a r e t u r n o f Osmpl t o normal v a l u e s , r a t h e r than d e h y d r a t i o n , s i n c e n e i t h e r Hct nor e l e c t r o l y t e c o n c e n t r a t i o n s i n c r e a s e d w i t h f u r t h e r i n c r e a s e s i n d r i n k i n g water s a l i n i t y . Other o s m o t i c a l l y a c t i v e p a r t i c l e s may c o n t r i b u t e t o the h i g h e r Osmpl i n g u l l s as p a r t o f t h e i r a d a p t a t i o n t o marine environments. U n l i k e g u l l s , ducks and geese s i g n i f i c a n t l y decreased body mass, and s i g n i f i c a n t l y i n c r e a s e d Hct, plasma e l e c t r o l y t e c o n c e n t r a t i o n s and Osmpl when d r i n k i n g water s a l i n i t y was 450 mM NaCl. T h i s suggests ducks were dehydrated because 52 i n s u f f i c i e n t f r e e water was e x t r a c t e d from i n g e s t e d s a l i n e by s a l t g l a n d s e c r e t i o n . The osmoregulatory c a p a c i t y of geese f e l l between those of ducks and g u l l s . In c o n t r a s t t o my o r i g i n a l h y p o t h e s i s (based on s a l i n e i n f u s i o n experiments) d u r i n g slow s a l i n e a c c l i m a t i o n a l l t h r e e s p e c i e s i n c r e a s e d [AVT] p l and decreased [Ang H ] p l without concomitant i n c r e a s e i n ECF t o n i c i t y and ECFV, r e s p e c t i v e l y . The a l t e r e d [AVT] p l and [Ang H ] p l would i n f l u e n c e kidney and s a l t g l a n d f u n c t i o n t o m a i n t a i n ECF t o n i c i t y and volume a t new steady s t a t e l e v e l s a f t e r each i n c r e a s e i n d r i n k i n g water s a l i n i t y . These r e s u l t s support the i d e a t h a t the r o u t e by which s a l t i s a d m i n i s t e r e d i n f l u e n c e s changes i n a b i r d ' s ECF volume and t o n i c i t y , [AVT] p l, [Ang I I ] p l , and, t h e r e f o r e , i t s r e s u l t a n t s a l t g l a n d and kidney f u n c t i o n . These f i n d i n g s a l s o suggest t h a t f a c t o r s o t h e r than h y p e r o s m o l a l i t y and hypovolemia a f f e c t the r e l e a s e of AVT and Ang I I i n b i r d s w i t h s a l t g l a n d s . These might be b l o o d p r e s s u r e , o r some undef i n e d i n t e r a c t i o n of ECFV, ECF t o n i c i t y and b l o o d p r e s s u r e . 53 APPENDIX 54 FIGURE 1. The amino acid sequence of a n t i d i u r e t i c hormone i n birds (arginine vasotocin, AVT) and mammals (arginine vasopressin, AVP), (from Koike, 1989 and Manning and Sawyer, 1985). Arginine Vasotocin, AVT CYS - TYR - ILEU - GLN - ASN - CYS - PRO - ARG - GLY - NH2 i I I I Arginine Vasopressin, AVP CYS - TYR - PHE - GLN - ASN - CYS - PRO - ARG - GLY - NH2 i i i i 55 FIGURE 2. The amino a c i d sequence o f a v i a n and mammalian a n g i o t e n s i n I I (Ang I I ) , (from Wilson, 1984). 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