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UBC Theses and Dissertations

The osmotic and ionic regulatory capacities of the kidney of the harbor seal, Phoca vitulina Tarasoff, Frederick John 1968

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THE OSMOTIC AND IONIC REGULATORY CAPACITIES OF THE KIDNEY OF THE HARBOR SEAL,.PHOCA VITULINA  by  FREDERICK JOHN TARASOFF  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n t h e Department of . Zoology  We a c c e p t t h i s t h e s i s as conforming t o t h e required standard  The U n i v e r s i t y o f B r i t i s h Columbia J u l y , 1968  In p r e s e n t i n g t h i s  thesis  f o r an advanced degree at  that  the  Study.  thesis  in p a r t i a l  for  Department  freely, available  requirements  for  I agree  r e f e r e n c e and  this  s c h o l a r l y purposes may be granted by the Head of my  or by hlis r e p r e s e n t a t i v e s .  thesis for  without my w r i t t e n p e r m i s s i o n .  of  ^OCUOGf  The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8 , Canada Date  the  agree that p e r m i s s i o n f o r e x t e n s i v e copying of  or p u b l i c a t i o n of t h i s  Department  of  the U n i v e r s i t y of B r i t i s h Columbia,  L i b r a r y sha11 make i t  I further  fulfilment  It  is understood that copying  financial  gain s h a l l not be allowed  ii  ABSTRACT  The mechanisms o f o s m o t i c and i o n i c r e g u l a t i o n i n marine mammals a r e o f i n t e r e s t because o f t h e a p p a r e n t l a c k o f " f r e s h " water i n t h e i r environment. i n v e s t i g a t i o n on t h e harbor s e a l ,  Previous  (pjhoca v i t u l i n a , L.) /  g e n e r a l l y i n d i c a t e d t h a t t h e s e a l can o b t a i n a l l t h e water i t r e q u i r e s from i t s f o o d .  However, some d i s p u t e  still  e x i s t s as t o whether t h e s e a l may i n g e s t sea water a l o n g w i t h i t s f o o d and conserve water by c o n c e n t r a t i n g i o n s and e x c r e t i n g them w i t h a n e t water g a i n . The e f f e c t s o f a 16-hour p e r i o d w i t h no f l u i d s and a l s o o f i n t u b a t i o n w i t h v a r y i n g amounts o f d i s t i l l e d water and v a r y i n g amounts and c o n c e n t r a t i o n s o f sea water were determined.  The c o n c e n t r a t i o n s o f sodium, c h l o r i d e and  p o t a s s i u m i o n s as w e l l as t h e o s m o t i c p r e s s u r e s o f plasma and u r i n e were measured f o r t h e p e r i o d s b e f o r e and a f t e r intubation. The r e s u l t s o f t h i s s t u d y a r e d i s c u s s e d w i t h r e s p e c t t o p u b l i s h e d d a t a and proposed mechanisms o f o s m o t i c and i o n i c r e g u l a t i o n by the kidney.  The f i n d i n g s i n d i c a t e , as  suggested by o t h e r s , t h a t t h e s e a l does n o t g a i n any s u b s t a n t i a l amount o f water from sea water i n g e s t i o n .  iii  TABLE OF CONTENTS Page INTRODUTION  1  MATERIALS AND METHODS  6  (i) Animals  6  ( i i ) Sampling p r o c e d u r e  6  ( i i i ) A n a l y t i c a l procedure  8  RESULTS  10  DISCUSSION  29  SUMMARY  40  LITERATURE CITED  41  iv  LIST OF TABLES  Table  I  Page  P e r c e n t a g e o f i n p u t o f volume, c h l o r i d e , sodium and p o t a s s i u m e x c r e t e d i n 13 hours.  II  26  Maximum v a l u e s r e c o r d e d f o r u r i n e o s m o l a l i t y and c h l o r i d e , sodium and p o t a s s i u m i o n concentrations.  27  LIST OF FIGURES  Figure 1  Page Changes i n plasma o s m o l a l i t y (mOsm./l.), w i t h time.  2  Changes i n u r i n e o s m o l a l i t y (mOsm./l.) and s p e c i f i c g r a v i t y w i t h time.  2 (b) 3  12  Changes i n u r i n e o s m o l a l i t y (mOsm./l.) and s p e c i f i c g r a v i t y w i t h time.  13  Changes i n plasma c h l o r i d e c o n c e n t r a t i o n (mEq./l.) w i t h time.  4  11  16  Changes i n plasma sodium c o n c e n t r a t i o n (mEq./l.) w i t h time.  17  5  Changes i n u r i n e volume (ml.) w i t h time.  19  6  Changes i n u r i n e c h l o r i d e c o n c e n t r a t i o n (mEq./l.) w i t h time.  7  Changes i n u r i n e sodium i o n c o n c e n t r a t i o n (mEq./l.) w i t h time.  8  20  22  Changes i n u r i n e p o t a s s i u m i o n c o n c e n t r a t i o n (mEq./l.) w i t h time.  24  vi  ACKNOWLEDGMENT  I w i s h t o e x p r e s s my thanks t o Dr. H.D. F i s h e r who has a s s i s t e d and s u p e r v i s e d t h i s p r o j e c t . My g r a t i t u d e i s a l s o extended t o D r s . P.A. Dehnel, J.E. P h i l l i p s and l a b o r a t o r y  and D.T. S u z u k i f o r t h e use o f equipment facilities.  I would a l s o l i k e t o thank Mr. Dan Toews, M i s s E l s p e t h McGowan and my w i f e , Mary f o r t e c h n i c a l a s s i s t a n c e .  INTRODUCTION  The p h y s i o l o g i c a l a d a p t a t i o n s o f marine mammals t o t h e i r environment have been o f i n t e r e s t t o b i o l o g i s t s f o r some time and have been r e c e n t l y r e v i e w e d by H a r r i s o n and Tomlinson (1961), L i l l y  (1964), S c h o l a n d e r (1964) and Andersen  (1966).  The q u e s t i o n o f o s m o t i c and i o n i c r e g u l a t i o n has been o f p a r t i c u l a r i n t e r e s t because o f t h e apparent l a c k o f " f r e s h " water a v a i l a b l e t o t h e s e a n i m a l s . W i t h r e f e r e n c e t o water b a l a n c e and o s m o t i c r e g u l a t o r y mechanisms, t h e most e x t e n s i v e l y s t u d i e d marine mammal has been t h e harbor s e a l , phoca v i t u l i n a .  T h i s s e a l has been  found c o n s i d e r a b l e d i s t a n c e s up r i v e r s and i n e s t u a r i e s a l t h o u g h t h e v a s t m a j o r i t y l i v e s e n t i r e l y i n a marine environment  ( F i s h e r , 1952 and S c h e f f e r , 1958).  Those harbor  s e a l s i n f r e s h and e s t u a r i n e h a b i t a t s have an abundant supply o f f r e s h water.  However, t o renew i t s body w a t e r ,  a s e a l which l i v e s i n sea water would have t o m i g r a t e t o r i v e r mouths p e r i o d i c a l l y t o d r i n k f r e s h water, d r i n k sea water and e x c r e t e a h y p e r t o n i c u r i n e , o r o b t a i n water from the m e t a b o l i c breakdown o f i t s f o o d .  Periodic migration to  f r e s h water seems u n l i k e l y i n v i e w o f o b s e r v a t i o n s by t h e a u t h o r o f some s e a l s s u r v i v i n g w i t h o u t f r e s h water on i s l a n d s i n a marine s e t t i n g , f o r example P r i b i l o f Irving, et a l .  Islands.  (1935) examined t h e c h l o r i d e c o n t e n t  o f u r i n e and f e c a l m a t t e r from twenty young harbor s e a l s k e p t i n sea water and d e t e r m i n e d t h a t t h e c h l o r i d e c o n t e n t was comparable t o t h a t o f t e r r e s t r i a l mammals.  They  2  c o n c l u d e d t h a t the s e a l d i d not d r i n k sea water and s e a l ' s k i d n e y was  that  not unique i n i t s a b i l i t y t o e x c r e t e  the  salt.  From c a l c u l a t i o n s i n v o l v i n g the amount o f water a v a i l a b l e from m e t a b o l i s m o f h e r r i n g and  the p o s s i b l e p h y s i o l o g i c a l  uses o f t h i s water, t h e y c o n c l u d e d t h a t the harbor s e a l c o u l d manage a d e q u a t e l y on the water from i n g e s t e d  fish.  Smith (1936) examined the i n o r g a n i c c o m p o s i t i o n o f u r i n e and one  the  the c o m p o s i t i o n o f s a l t s o f r e c t a l washings o f  c a p t i v e harbor s e a l .  not s w a l l o w any  Smith c o n c l u d e d t h a t the s e a l d i d  considerable  q u a n t i t y o f sea water.  on the b a s i s of I r v i n g ' s work and h i s own water and water f o r u r i n e f o r m a t i o n the food.and from m e t a b o l i s m .  r e s u l t s , t h a t body  a r e d e r i v e d from water i n  Albrecht  (19 50)  intubated  harbor s e a l s w i t h sea water and a f t e r o b s e r v i n g o f the a n i m a l s ,  He assumed,  the  reactions  v o m i t i n g and d i a r r h e a , c o n c l u d e d t h a t they do  not d r i n k sea w a t e r .  She  a l s o d e h y d r a t e d the a n i m a l s  and  o b s e r v e d t h a t the s e a l s c o u l d not be i n d u c e d t o d r i n k  sea  water. F r e s h water d r i n k i n g has been r e p o r t e d by I r v i n g , e t a l . (1935) and A l b r e c h t  (1950) and has been o b s e r v e d i n newly  a r r i v e d s e a l s o f the U.B.C. c o l o n y . o f the s e a l s had o c c u r r e d  In a l l c a s e s ,  p r i o r to d r i n k i n g .  However, these  s e a l s have never been o b s e r v e d t o d r i n k sea w a t e r . be assumed t h a t the s e a l does not d r i n k sea w a t e r , q u e s t i o n o f how considered. 1100  dehydration  I f i t can the  i t c o n s e r v e d i t s s u p p l y o f water s h o u l d  I r v i n g , e_t a_l. (193 5) c a l c u l a t e d t h a t o f  grams o f water y i e l d e d by 1250  grams of h e r r i n g ,  be the 300  3  grams would be used f o r p e r s p i r a t i o n , r e s p i r a t i o n and f o r m a t i o n o f f e c e s , and the r e m a i n i n g a v a i l a b l e for urine formation. sweat g l a n d s ,  the  800 grams would be  A l t h o u g h the s e a l does have  I r v i n g , e_t al_. (193 5) assumed t h a t e v a p o r a t e d  water from p e r s p i r a t i o n i s not n e c e s s a r y f o r  thermal  r e g u l a t i o n s i n c e the a n i m a l r e s i d e s i n a c o o l a q u a t i c habitat. al.  Smith (1936), H i a t t and H i a t t (1942) and Page, e t  (19 54) o b s e r v e d an i n c r e a s e i n u r i n e volume i n the s e a l  a f t e r a meal o f h e r r i n g and a decrease i n u r i n e f l o w between feedings.  The  H i a t t s s u g g e s t e d t h a t the k i d n e y  activity  i n c r e a s e s when t h e r e i s water t o spare f o r e x c r e t i o n  and  d e c r e a s e s between meals i n o r d e r t o conserve w a t e r .  The  Hiatts  f u r t h e r suggested t h a t post-feeding r e n a l v a s o d i l a t i o n occurs o n l y when water i s a v a i l a b l e , v a s o c o n s t r i c t i o n and associated r e d u c t i o n i n glomerular e x c r e t i o n at other times.  filtration  l i m i t i n g water  They p o s t u l a t e d t h a t i t was  r e d u c t i o n o f b l o o d f l o w i n the k i d n e y s ,  this  and not the change  i n the number o f a c t i v e g l o m e r u l i , t h a t was the r e d u c e d u r i n e  the  responsible for  output.  D i v i n g and i t s a s s o c i a t e d r e d u c t i o n o f b l o o d f l o w to v a r i o u s organs has been shown t o p l a y an i m p o r t a n t c o n s e r v i n g body w a t e r .  I r v i n g , e t a l , (1935) i n i t i a l l y  demonstrated t h a t d u r i n g d i v i n g t h e r e was p e r i p h e r a l b l o o d f l o w i n the s e a l . Bing  role in  a decrease i n  F u r t h e r m o r e , Bradley' and  (1942) found t h a t d u r i n g d i v i n g t h e r e was  marked  v a s o c o n s t r i c t i o n o f a r t e r i e s l e a d i n g t o the k i d n e y s a l m o s t complete c e s s a t i o n o f g l o m e r u l a r  with  f i l t r a t i o n and  urine  4  formation.  They c o n c l u d e d t h a t the i n t r a - r e n a l  v a s o c o n s t r i c t i v e response t o apnea appears  to i n v o l v e both  a f f e r e n t and e f f e r e n t . a r t e r i o l e s i n a r e l a t i v e l y u n i f o r m manner.  B r a d l e y , e_t al_.  (1954) observed t h a t sodium,  p o t a s s i u m and water e x c r e t i o n d e c r e a s e d g r e a t l y w i t h r e d u c t i o n i n f i l t r a t i o n d u r i n g apnea.  Lowrance, e t a l . (1956) compared  the e f f e c t s o f a n o x i a and apnea i n the harbor s e a l and c o n c l u d e d t h a t they have comparable e f f e c t s on r e n a l a c t i v i t y . D u r i n g d i v i n g t h e r e i s a stoppage o f b r e a t h i n g and  consequently  no water l o s t by e v a p o r a t i o n from the l u n g s . A h i s t o l o g i c a l e x a m i n a t i o n o f the nephrons o f the k i d n e y o f the harbor s e a l has not been attempted.  However, Sperber  (1944) has examined nephrons o f two c l o s e l y r e l a t e d p i n n i p e d s , Phoca b a r b a t a and Phoca h i s p i d a .  The l e n g t h o f the l o o p s o f  Henle and m e d u l l a r y t h i c k n e s s i n these two s e a l s were comparable t o those o f t e r r e s t r i a l c a r n i v o r e s , t h e r e b y s u p p o r t i n g the p h y s i o l o g i c a l d a t a o f I r v i n g , e_t al_. t h a t these a q u a t i c a n i m a l s can form a hyperosmotic  (193 5) urine,  b u t not as c o n c e n t r a t e d as would be e x p e c t e d i f they  drank  sea w a t e r . S e v e r a l i n v e s t i g a t o r s have answered, i n p a r t , the q u e s t i o n whether the s e a l can conserve water from sea water by f o r m i n g a hyperosmotic u r i n e .  A l b r e c h t (1950) r e c o r d e d the h i g h e s t  u r i n e c h l o r i d e i o n c o n c e n t r a t i o n a f t e r i n t u b a t i n g sea water.  From her graph the v a l u e would be a p p r o x i m a t e l y  m i l l i e q u i v a l e n t s per l i t e r (mEq./l.),.  500  The h i g h e s t u r i n e  sodium and p o t a s s i u m v a l u e s r e p o r t e d i n the l i t e r a t u r e a r e  5  480 and 370 mEq.l., r e s p e c t i v e l y ( B r a d l e y , e t a l , 1954). These v a l u e s i n d i c a t e t h a t t h e s e a l cannot e x c r e t e a l l o f these i o n s i n u r i n e a t c o n c e n t r a t i o n s  h i g h e r than those o f  open sea w a t e r ( c h l o r i d e : 548.3; sodium: 470.2; p o t t a s i u m : (Barnes,  9.9  1954)).  I n t h e harbor s e a l n e i t h e r t h e o s m o t i c and i o n i c r e g u l a t o r y c a p a c i t i e s o f t h e k i d n e y , nor t h e e x c r e t o r y  patterns  f o l l o w i n g i n g e s t i o n o f s e a water have been f u l l y examined. In t h i s study t h e e f f e c t s o f d e h y d r a t i o n  o f t h e s e a l and  i n t u b a t i o n o f d i s t i l l e d water and o f s e a water i n v a r y i n g volumes and c o n c e n t r a t i o n s were examined and t h e f o l l o w i n g points considered: concentrations  1.  t h e u r i n e volumes and t h e  o f sodium, c h l o r i d e and p o t a s s i u m i n t h e plasma  and u r i n e over a p e r i o d o f t h i r t e e n hours a f t e r i n t u b a t i n g d i s t i l l e d water and s e a w a t e r . pressures  2.  t h e maximum u r i n e o s m o t i c  and t h e maximum sodium, c h l o r i d e and p o t a s s i u m  concentrations  t h a t t h e k i d n e y o f t h e harbor s e a l i s c a p a b l e  of producing.  3.  the source o f water, e i t h e r ingested or  produced from body-water r e s e r v e s , which i s used t o e l i m i n a t e the ions  ingested.  C o n s i d e r a t i o n o f these problems w i l l h e l p determine whether t h e k i d n e y  has any s p e c i a l o s m o t i c o r i o n i c  regulatory adaptations marine environment.  t h a t enable the s e a l to s u r v i v e i n the  6 MATERIALS AND METHODS  ANIMALS:  Two y e a r l i n g female harbor s e a l s c a p t u r e d o f f  N o r t h e r n Vancouver period.  I s l a n d were s t u d i e d over a one year  The s e a l s were k e p t i n wood-stave t a n k s , n i n e f e e t  i n d i a m e t e r , which c o n t a i n e d two f e e t o f r u n n i n g f r e s h water. Over t h e t e s t p e r i o d t h e y were each f e d about f i v e pounds of  thawed h e r r i n g d a i l y and m a i n t a i n e d t h e i r w e i g h t s a t  9 5 + 8 pounds. SAMPLING PROCEDURE:  To ensure t h a t t h e s e a l s were i n a  p o s t - a b s o r p t i v e s t a t e , they were s t a r v e d f o r 3 6 hours p r i o r to an e x p e r i m e n t .  One hour a f t e r removing t h e a n i m a l from i t s  tank and r e s t r a i n i n g i t , t h e f i r s t u r i n e sample was t a k e n and o n e - h a l f hour l a t e r t h e f i r s t b l o o d sample was t a k e n . Over t h e n e x t 16 hours, t h e presence o f f l u i d around t h e eyes, mouth and n o s t r i l s were r e c o r d e d h o u r l y .  The room  temperature was m a i n t a i n e d a t 67 t 2°F. The f o l l o w i n g f l u i d s were i n t u b a t e d i n i n d i v i d u a l e x p e r i m e n t s two hours a f t e r t h e i n i t i a l u r i n e  collection:  500 m l . and 1000 m l . o f d i s t i l l e d water; 500 ml., 750 m l . and 1000 m l . o f s e a water; and 750 m l . o f s e a water w h i c h had been e v a p o r a t e d t o g i v e 1.5 times t h e normal sea water c o n c e n t r a t i o n s o f t h e i o n s t o be s t u d i e d  {1-h x S.W.).  In a c o n t r o l experiment, t o determine t h e e f f e c t s o f d e h y d r a t i o n and s t r e s s d u r i n g t h e 16 hour c o l l e c t i o n p e r i o d , the  a n i m a l was r e s t r a i n e d and sampled i n t h e above manner,  b u t no f l u i d was i n t u b a t e d .  The c o n t r o l experiment was done  once f o r each a n i m a l and was t h e f i r s t t e s t c a r r i e d o u t .  7  a.  Urine C o l l e c t i o n :  The  h i n d f l i p p e r s of the s e a l were  s t r a p p e d t o the r e s t r a i n i n g b o a r d . (3.5" i n l e n g t h and 1.5"  A p l e x i g l a s s speculum  i n diameter) was  placed into  u r o g e n i t a l v e s t i b u l e as f a r as the u r i n a r y p a p i l l a . s t e r i l e X-ray c a t h e t e r was and the u r i n e was (Whirlpac Co.).  then i n s e r t e d i n t o the  the A  bladder  c o l l e c t e d i n a s t e r i l e polyethylene  bag  A f t e r r e c o r d i n g the volume, the u r i n e  pipetted into containers for a n a l y s i s . the f l i p p e r s were f r e e to move.  was  Between c o l l e c t i o n s  A g l a s s d i s h was  placed to  c a t c h any u r i n e or f e c a l m a t e r i a l v o i d e d between  sampling  times. b.  Blood C o l l e c t i o n :  was  removed and the s k i n scrubbed w i t h an a n t i s e p t i c  and w i t h 70% e t h a n o l .  The  h a i r above two  lumbar  vertebrae  In t h i s r e g i o n a l o c a l a n e s t h e t i c  (10 m l . of 1% x y l o c a i n e ) was  injected intramuscularly.  18-gauge t h i n - w a l l e d n e e d l e w i t h f i t t e d s t y l e t was between two n e u r a l s p i n e s of the v e r t e b r a e i n t o intravertebral-epidural vein. a s t e r i l e polyethylene canula the n e e d l e was  The  s t y l e t was  inserted  replaced with  ( I n t r a m e d i c PE 50) and  removed l e a v i n g the c a n u l a i n p l a c e .  sodium h e p a r i n s o l u t i o n .  An  the  p r e v e n t b l o o d from c l o t t i n g i n the c a n u l a , i t was w i t h a 0.1%  (Phisohex)  B l o o d was  then To  filled  withdrawn  i n a h e p a r i n i z e d 10 ml. d i s p o s a b l e s y r i n g e from which the l i q u i d h e p a r i n had been f o r c i b l y removed. was  A 21-gauge n e e d l e  used t o connect the s y r i n g e to the c a n u l a .  A f t e r each  8  10 m l . b l o o d sample was with heparin.  c o l l e c t e d , the c a n u l a was  The whole b l o o d was  minutes a t 3 500rpm and  filled  c e n t r i f u g e d f o r 25  the plasma p i p e t t e d i n t o c o n t a i n e r s  for a n a l y s i s . ANALYTICAL PROCEDURES: a.  Osmotic P r e s s u r e :  Two  milliliter  a l i q u o t s o f each u r i n e  and plasma sample were p i p e t t e d i n t o osmometer tubes. number of m i l l i o s m o l e s was (Model G-62)  :  The  d e t e r m i n e d on a F i s k e Osmometer  which had been c a l i b r a t e d u s i n g p r e p a r e d sodium  c h l o r i d e s t a n d a r d s so t h a t d i r e c t r e a d i n g s r a n g i n g from 0 t o 3 000 m i l l i o s m o l e s c o u l d be t a k e n .  The  w i t h i n f o u r hours a f t e r the c o m p l e t i o n b.  C h l o r i d e Ion D e t e r m i n a t i o n :  The  i n the u r i n e and plasma samples was Buchler-Cotlove  chloridometer.  samples were  o f each e x p e r i m e n t .  chloride ion  concentration  determined using a  S o l u t i o n s were p r e p a r e d by  combining 0.1 ml. of sample w i t h 4 ml. o f a r e a g e n t (0.1 N HNO3 and  analysed  nitric-acetic  10% g l a c i a l a c e t i c a c i d ) .  were p r e p a r e d f o r b o t h HIGH and LOW  Standards  r a t e s of t i t r a t i o n  by  a d d i n g 0.1 m l . o f 104 mEq./l. and 0.1 m l . o f 1 mEq./l. sodium c h l o r i d e s o l u t i o n , r e s p e c t i v e l y , > t o 4 ml. of  the  n i t r i c - a c e t i c a c i d reagent.  of  Method b l a n k s o f 4 ml.  n i t r i c - a c e t i c a c i d r e a g e n t were a l s o p r e p a r e d . t i t r a t i o n 0.2 to each c.  Before  ml. o f g e l a t i n p H - i n d i c a t o r s o l u t i o n was  added  vial.  Sodium Ion D e t e r m i n a t i o n :  were p r e p a r e d by d i l u t i n g 1  Samples of u r i n e and o f sample i n 5 ml.  d i s t i l l e d , d e m i n e r a l i z e d water i n p o l y e t h y l e n e  plasma of  vials  9  (Nalgene Co.).  P r e p a r e d samples were f r o z e n and s t o r e d a t  -10°c. u n t i l the sodium i o n c o n c e n t r a t i o n c o u l d be determined. diluting  Sodium c h l o r i d e s t a n d a r d s were p r e p a r e d by  1 j u l . of stock solutions i n 5 ml. of d i s t i l l e d ,  d e m i n e r a l i z e d water and were used t o c a l i b r a t e t h e Unicam flame photometer curve.  (Model SP9 00) and t o o b t a i n a s t a n d a r d  Samples were a n a l y z e d on the flame photometer and  the  sodium i o n c o n c e n t r a t i o n (mEq./l.) was determined from  the  standard curve.  d.  Potassium Ion Determination:  were p r e p a r e d by d i l u t i n g  Samples o f u r i n e and plasma  50 /xl. o f sample i n t o 5 m l . o f  d i s t i l l e d , d e m i n e r a l i z e d water.  The p r e p a r e d samples were  f r o z e n and s t o r e d a t -10°C. u n t i l t h e c o n c e n t r a t i o n s c o u l d be determined.  The Unicam flame photometer  was c a l i b r a t e d  u s i n g 50 / x i . o f K C l s t a n d a r d s d i l u t e d i n 5 m l . o f water. P o t a s s i u m i o n c o n c e n t r a t i o n s i n t h e samples were determined from t h e s t a n d a r d curve which ranged from 0 t o 275 mEq./l. "Lab-trol"  (Dade Reagents  I n c . ) , a c o n t r o l serum i n l i q u i d  form c o n t a i n i n g known c o n c e n t r a t i o n s o f substances found i n the  b l o o d , was used i n a l l c h l o r i d e , sodium and p o t a s s i u m  i o n d e t e r m i n a t i o n s as a s t a n d a r d .  10 RESULTS  I n i t i a l l y , t h r e e s e a l s were chosen f o r s t u d y , however, one  a n i m a l was unable t o t a k e t h e s t r e s s o f t h e e x p e r i m e n t a l  c o n d i t i o n s and gave v e r y e r r a t i c r e s u l t s o r became i l l during the experiments. two  s e a l s c o u l d be used.  Thus, i n t h e f i n a l a n a l y s i s , o n l y A l t h o u g h t h e q u a l i t a t i v e responses  of t h e two s e a l s a r e s i m i l a r , t h e r e a r e o b v i o u s q u a n t i t a t i v e differences.  The changes i n plasma o s m o l a l i t y p r i o r t o and  f o l l o w i n g i n t u b a t i o n o f f l u i d s a r e shown i n F i g u r e s  la-lg.  Each o f t h e i n t u b a t i o n e x p e r i m e n t s was compared t o t h e c o n t r o l i n which no f l u i d was g i v e n .  I t can be n o t e d t h a t t h e  p r e i n t u b a t i o n v a l u e s v a r i e d between 318 and 33 0 mOsm./l. f o r s e a l #1 and between 318 and 343 mOsm./l. f o r s e a l #2. I n t u b a t i o n o f 500 m l . o f d i s t i l l e d water and 500, 750 and 1000  m l . o f sea water does n o t appear t o have any g r e a t  e f f e c t on t h e o s m o l a l i t y o f t h e plasma i f one c o n s i d e r s t h e changes from t h e p r e i n t u b a t i o n v a l u e s and t h e changes observed i n the c o n t r o l .  However, 1000 m l . o f d i s t i l l e d  water d e c r e a s e d t h e o s m o l a l i t y o f t h e plasma t o as low as 305 mOsm./l. ( S e a l #1) and 308 mOsm./l. ( S e a l #2).  W i t h 750  m l . o f 1^ x sea water t h e o s m o l a l i t y o f t h e plasma  increased  for  gradually  3-4  hours a f t e r i n t u b a t i o n and then r e t u r n e d  to the p r e i n t u b a t i o n  values.  In a n a l y s i n g t h e u r i n e o s m o l a l i t y  ( F i g u r e 2a-2g), i t can  be seen t h a t d u r i n g t h e c o n t r o l t e s t s , S e a l #2 had a much higher osmotic pressure  than S e a l #1.  A f t e r d i s t i l l e d water  i n g e s t i o n , t h e s e a l s responded s i m i l a r l y w i t h t h e  FIGURE 1:  Changes i n plasma o s m o l a l i t y (mOsm./l.). Intubation a t 0 time.  a.  Control  b.  500 m l . d i s t i l l e d water  c.  1000 m l . d i s t i l l e d water  d.  500 m l . sea water  e.  7 50 m l . sea water  f.  1000 m l . sea water  g.  750 m l . 1% x sea water  S e a l #1 S e a l #2  11  350r  325b  350  a 300  325k 350r  300LJ  .I i i i si i i i i i i i• 0 4 8 . 1 2  350r  E co O  325  <b  300  L. =3  •i  ... i  i  , »  1  I  I  L_  0  12  CO CO  325  300L,  6  <D  i  L  _1  i  Q. U -t-J  i—  12  O  350r L 325  CO  o 350  300Li  325 350r  300  12  Time -(hours)  '  i  I  1  I  I  I  1  I  I  L_  12  g  325  30QI  . i l . . — i — -  0  4  —1  1  8  1  I  I  '  12  '  FIGURE 2:  Changes i n u r i n e o s m o l a l i t y (mOsm./l.) and specific  gravity.  I n t u b a t i o n a t 0 time.  a.  Control  b.  500 m l . d i s t i l l e d water  c.  1000 m l . d i s t i l l e d  S e a l #1 S e a l #2  water  12  1900r  a  1.3550  1.3450  1.3350 ' ' Q d) L. ZJ  1 1 1  ^  8  12  +->  >  1900  a  I/) (D  1.3550!  U)  L.  1.3450  1200h  U  o E  5001  CO  0  12  0  12  O 1900r  1.3550r  1200h  1.3450  500  L  12  1.335 0  1  Ti m e ( h o u r s )  FIGURE 2 ( b ) : Changes i n u r i n e o s m o l a l i t y (mOsm./l.) and s p e c i f i c g r a v i t y . 0 time.  d.  500 m l . sea water  e.  750 m l . sea water  f.  1000 m l . sea water  g.  750 m l . lJg x s e a water  S e a l #1 S e a l #2  -  Intubation at  Osmotic  00 O 01  O  J  ^  .  U>  Cn O  CO  cn Cn O  OJ OJ  Cn O  OJ  Cn O  pressure  W  cn Cn O  OJ  co <-n O  (mOsm./l.)  C  Cn O  O  W  (j, Cn O  OJ  co Cn O  OJ  ^ Cn O  OJ  Cn Cn O  14  osmolality  decreasing  In b o t h t h e water, after in One  within  tests with  500  ml.  hour f o l l o w i n g  and  1000  ml.  the  former  then s t a r t e d to i n c r e a s e  c a s e and  a f t e r another  hour f o l l o w i n g t h e  gave d i f f e r e n t was  no  sea water,  S e a l #2  experiment.  and  1000  ml.  i n g e s t i o n of  r e s u l t s f o r the  overall  the  in  and  500  increased  1000  increasing  ml.  test.  of  sea  in  the  750  S e a l #2. results  150  750  ml.  f o r 500  of  1^  sea water  and was  and  1000  t e s t s there  preintubation to a higher  less overall S e a l #2  ml.  sea  value.  increased  of  throughout 7 50  x sea  g r a v i t y of  2a-2g a l s o show t h e the  urine  For  200  and  c o n t r o l and  t h e s e two  values  however, t h e r e  distilled are  very  with  Seal  In t h e  1%  x  t i m e s and  an  no  (Seal  increase  the osmolality.  the  specific  osmolality. the  trends  With sea water  specific  s e c o n d hour a f t e r i n t u b a t i o n , b u t  sea  600-700 mOsm./l. f o r  water experiments,  i s a drop i n the  #2  mOsm./lJ, whereas  change i n p l a s m a  similar.  the  increase  r e l a t i o n s h i p between  at d i f f e r e n t  ml.  water  overall  w a t e r t e s t s t h e r e was  large overall  #1  change i n o s m o l a l i t y  mOsm./l. f o r S e a l #1  i n d i c a t e d no  seals  ml.  similar.  i s an value  two  With Seal  i t s urine osmolality  w a t e r , and  latter.  A l t h o u g h t h e r e were i n d i v i d u a l v a r i a t i o n s ,  Figure  In t h e  100  and  of at l e a s t  in  ml.  tests there  increased  the  However, f o l l o w i n g i n t u b a t i o n o f  earlier  #1  5 hours  immediately  sea water,  change i n o s m o l a l i t y  o s m o l a l i t y above the  water  distilled  5 hours i n the  e x p e r i m e n t s t h e r e s u l t s were q u a l i t a t i v e l y 7 50  of  intubation.  the o s m o l a l i t y r e a c h e d t h e minimum v a l u e i n t u b a t i o n and  there  one  tests,  gravity within  corresponding  the  drop i n  15  the o s m o l a l i t y .  By the end o f the sampling  time,  the  s p e c i f i c g r a v i t y had i n c r e a s e d and the u r i n e o f S e a l #2  had  the h i g h e r s p e c i f i c g r a v i t y and a l s o the h i g h e r o s m o t i c pressure.  The  s p e c i f i c g r a v i t y v a l u e s as a r e f l e c t i o n of  t o t a l s o l i d s i n the u r i n e may  h e l p account f o r the  o s m o l a l i t y changes o b s e r v e d . The  c h l o r i d e c o n c e n t r a t i o n s i n the plasma samples were  d e t e r m i n e d and a r e p r e s e n t e d  i n F i g u r e 3a-3g.  In comparing  the p a t t e r n s o f changes i n c o n c e n t r a t i o n s t o t h a t of  the  c o n t r o l , i t can be seen t h a t no o b v i o u s d i f f e r e n c e s occur f o l l o w i n g d i s t i l l e d water i n t u b a t i o n .  However, w i t h i n g e s t i o n  o f sea w a t e r , the c h l o r i d e i o n c o n c e n t r a t i o n appears t o be i n c r e a s e d over the p r e i n t u b a t i o n values i n b o t h s e a l s . Changes i n plasma sodium c o n c e n t r a t i o n s are shown i n F i g u r e 4a-4g.  Again,  152 and 172 m E q . / l . ) .  the p r e i n t u b a t i o n v a l u e s v a r y There appear  (between  t o be no measurable  e f f e c t s on the sodium c o n c e n t r a t i o n s f o l l o w i n g i n t u b a t i o n w i t h d i s t i l l e d water.  F u r t h e r sampling  i s necessary  to  determine i f the peaks i n the c o n c e n t r a t i o n a f t e r sea water i n g e s t i o n are s i g n i f i c a n t and r e p e a t a b l e .  F i g u r e s 4e-4g  i n d i c a t e t h a t the sodium i o n c o n c e n t r a t i o n f l u c t u a t e s as much as i t does i n the c o n t r o l and d i s t i l l e d water  experiments.  Plasma p o t a s s i u m c o n c e n t r a t i o n s were measured, b u t d i d not change g r e a t l y i n any o f the t e s t s , v a r y i n g between and 5.0 mEq./l.  No o b v i o u s p a t t e r n o f v a r i a t i o n was  4.3  detected.  The more i n t e r e s t i n g r e s u l t s were o b t a i n e d w i t h a n a l y s i s o f u r i n e volume and the c o n c e n t r a t i o n of sodium, c h l o r i d e and p o t a s s i u m i n the u r i n e f o l l o w i n g i n t u b a t i o n .  FIGURE 3:  Changes i n plasma c h l o r i d e c o n c e n t r a t i o n " . (mEq./l.) w i t h time.  I n t u b a t i o n a t 0 time.  a.  Control  b.  500 m l . d i s t i l l e d water  c.  1000 m l . d i s t i l l e d water  d.  500 m l . sea water  e.  7 50 m l . sea water  f.  1000 m l . sea water  g.  750 m l . lh x sea water  S e a l #1 S e a l #2  16  FIGURE 4:  changes i n plasma sodium (mEq./l-) w i t h time.  I n t u b a t i o n a t 0 time.  a.  Control  b.  500 m l . d i s t i l l e d water  c.  1000 m l . d i s t i l l e d water  d.  500 m l . sea water  e.  750 m l . sea water  f.  1000 m l . sea water  g.  750 m l . 1^ x sea water  S e a l #1 S e a l #2  concentration  18  The  u r i n e volumes a r e p r e s e n t e d i n F i g u r e 5a-5g.  The  average r a t e o f volume o u t p u t (ml./hour) i n t h e c o n t r o l , i n which no f l u i d was i n t u b a t e d , was 14.8 f o r S e a l #1 and 13v8 f o r S e a l #2.  I n t u b a t i o n o f 500 ml. o f d i s t i l l e d water  increased  the average e x c r e t i o n r a t e t o 26.9 and 19.1 ml./hour, and 1000  m l . i n c r e a s e d i t t o 38.1 and 27.7 ml./hour i n s e a l s  #1 and #2, r e s p e c t i v e l y .  The p a t t e r n was a g r a d u a l o v e r a l l  i n c r e a s e t o t h e maximum v a l u e i n t h e d i s t i l l e d water e x p e r i m e n t s o c c u r r i n g a t 4 o r 8 hours f o r 500 m l . and 10 o r 11 hours f o r 1000 ml.  I n t h e s e a water t e s t s , however,  d i u r e s i s o c c u r r e d w i t h i n t h e f i r s t two hours a f t e r i n t u b a t i o n , reaching  a maximum i n t h e t h i r d hour i n a l l cases  5d-5g), and then d e c r e a s i n g  (Figures  to preintubation values.  In the  sea water t e s t s , the maximum e x c r e t i o n r a t e v a r i e d i n d i r e c t p r o p o r t i o n w i t h t h e volume i n g e s t e d and t h e s a l t Figures  load.  5b and 5c show t h a t w i t h no s a l t l o a d , t h e volume  intubated i s a f a c t o r i n determining r a t e and F i g u r e s  t h e maximum e x c r e t i o n  5e and 5g i n d i c a t e t h e e f f e c t o f i n c r e a s i n g  the s a l t l o a d w i t h o u t changing t h e volume i n p u t . The  concentration  o f c h l o r i d e i o n i n t h e u r i n e , shown i n  F i g u r e s 6a-6g, v a r i e d from 0 t o 508 mEq./l. i n t h e experiments.  The l o w e s t v a l u e s were o b t a i n e d  during the  c o n t r o l t e s t s and a f t e r d i s t i l l e d water i n t u b a t i o n , and t h e h i g h e s t v a l u e s , a f t e r s e a water i n t u b a t i o n . the c h l o r i d e i o n c o n c e n t r a t i o n  In the c o n t r o l ,  d e c r e a s e d g r a d u a l l y from 13.1  to 5.2 mEq./l. f o r S e a l #1 and from 44.6 t o 2.8 mEq./l. f o r S e a l #2.  I n t u b a t i o n w i t h 500 m l . r e s u l t e d i n decreases from  FIGURE 5:  Changes i n u r i n e volume (ml.) w i t h I n t u b a t i o n a t 0 time.  a.  Control  b.  500 m l . d i s t i l l e d water  c.  1000 m l . d i s t i l l e d water  d.  500 m l . sea water  e.  750 m l . sea water  f.  1000 m l . sea water  g.  750 m l . 1^ x sea water  S e a l #1 S e a l #2  time.  FIGURE 6:  Changes i n u r i n e c h l o r i d e (mEq./l.) w i t h time.  I n t u b a t i o n a t 0 time.  a.  Control  b.  500 m l . d i s t i l l e d  c.  1000 m l . d i s t i l l e d  d.  500 m l . sea water  e.  750 m l . sea water  f.  1000 m l . sea water  g.  750 m l . 1^ x sea water  water  S e a l #1 Seal  #2  concentration  water  20  a  21  44.2 t o 1.1 mEq./l. i n S e a l #1, and from 20.3 t o 1.0 mEq./l. i n S e a l #2.  S i m i l a r l y , t h e r e were d e c r e a s e s a f t e r t h e  i n t u b a t i o n o f 1000 m l . o f d i s t i l l e d water  (24.1 t o 0.0 and  9.5 t o 0.1 mEq./l. i n S e a l s #1 and #2, r e s p e c t i v e l y ^  The  i n t e r e s t i n g e f f e c t s were o b t a i n e d a f t e r sea water i n t u b a t i o n . The maximum c h l o r i d e c o n c e n t r a t i o n i s o b t a i n e d w i t h i n t h e f i r s t t h r e e t o f i v e hours f o r normal sea water and i n t h e e i g h t h hour f o r % x s e a water and i s independent o f t h e amount o f f l u i d i n t u b a t e d o r s a l t l o a d ( F i g u r e s 6d-6g).  The  shape o f t h e graph v a r i e d s l i g h t l y depending on t h e amount and c o n c e n t r a t i o n o f sea water i n g e s t e d .  The c h l o r i d e i o n  c o n c e n t r a t i o n decreased, b u t d i d n o t r e t u r n t o the p r e i n t u b a t i o n v a l u e s a t any time d u r i n g t h e 13 hours. The changes i n sodium i o n c o n c e n t r a t i o n s shown i n F i g u r e s 7a-7g.  (mEq./l.) a r e  These a r e v e r y s i m i l a r t o those  obtained f o r chloride i o n concentration  ( F i g u r e s 6a-6g).  The  l o w e s t v a l u e s o c c u r r e d i n t h e c o n t r o l t e s t s and f o l l o w i n g d i s t i l l e d water i n t a k e .  The range o f v a l u e s over t h e 13  hours i n t h e c o n t r o l , 500 m l . and 1000 m l . d i s t i l l e d a r e as f o l l o w s :  water  72.0 t o 9.5 (#1) and 34.0 t o 13.0 (#2);  49.0 t o 8.0 (#1) and 75.0 t o 24.5 (#2); 33.0 t o 6.0 (#1) and 65.0 t o 6.0 (#2), r e s p e c t i v e l y . F o l l o w i n g sea water i n t u b a t i o n , t h e maximum c o n c e n t r a t i o n o f sodium e x c r e t e d was o b t a i n e d w i t h i n t h e f i r s t t h r e e t o f o u r hours a f t e r i n t u b a t i o n and t h i s v a l u e was a p p r o x i m a t e l y 500 mEq./l.) ingested.  t h e same (470 t o  r e g a r d l e s s o f t h e amount o f c o n c e n t r a t i o n  A l s o , as i n t h e c h l o r i d e i o n a n a l y s e s , t h e r e a r e  FIGURE 7:  Changes i n u r i n e sodium i o n c o n c e n t r a t i o n (mEq./l.).  I n t u b a t i o n a t 0 time.  a.  Control  b.  500 ml. d i s t i l l e d water  c.  1000 m l . d i s t i l l e d water  d.  500 m l . sea water  e.  750 ml. sea water  f.  1000 m l . sea water  g.  7 50 m l . 1% x sea water S e a l #1  —  S e a l #2  —  22  23  some d i f f e r e n c e s i n t h e s h a p e s o f t h e c u r v e s , b u t o n t h e b a s i s o f t h e t e s t s done, i t i s n o t known w h e t h e r t h e s e a r e significant.  Following  1*2 x s e a w a t e r i n t u b a t i o n , b o t h t h e  c h l o r i d e and sodium c o n c e n t r a t i o n s . r e a c h e d concentrations values  The Figures  As  maximum  l a t e r and remained c l o s e r t o t h e i r  maximum  f o r the l a t t e r p a r t o f the t e s t p e r i o d than the other  sea water  those  their  experiments. r e s u l t s of potassium analyses  8a-8g.  are presented i n  I t i s r e a d i l y seen t h a t they d i f f e r  patterns obtained  from  i n t h e sodium and c h l o r i d e a n a l y s e s .  i n t h e c a s e o f u r i n e o s m o l a l i t y , S e a l #2 a p p e a r s t o h a v e  higher  values  t h a n S e a l #1 i n t h e c o n t r o l .  n o t p o s s i b l e t o know w i t h o u t  doing  However, i t i s  f u r t h e r experiments  whether t h e c o n t r o l values a r e r e p e a t a b l e .  The a v e r a g e  v a l u e o f p o t a s s i u m i o n c o n c e n t r a t i o n d i d n o t appear t o change d r a s t i c a l l y i n the d i s t i l l e d those  w a t e r t e s t s when c o m p a r e d t o  o f t h e c o n t r o l f o r S e a l #1, w h e r e a s , f o r S e a l #2 t h e  c o n t r o l v a l u e s w e r e v e r y much h i g h e r water t e s t s . in  than i n the d i s t i l l e d  The i n g e s t i o n o f 500 m l . o f s e a w a t e r r e s u l t e d  an i n c r e a s e i n ^ p o t a s s i u m i o n c o n c e n t r a t i o n a f t e r  4 hours.  T h i s c o u l d be r e l a t e d t o t h e decreased sodium i o n concentration  (Figure 7d).  In the other  sea water  experiments,  the potassium i o n c o n c e n t r a t i o n tended e i t h e r t o remain constant  o r t o decrease s l i g h t l y 4 hours a f t e r i n t u b a t i o n ,  e x c e p t w i t h S e a l #1 a f t e r In t h i s study,  750 m l . s e a w a t e r i n g e s t i o n .  one q u e s t i o n o f i n t e r e s t i s w h e t h e r t h e  functioning of the kidney  and o f t h e body e x c r e t i o n systems  EIGURE 8:  Changes i n u r i n e p o t a s s i u m i o n c o n c e n t r a t i o n (mEq./l.) w i t h time.  I n t u b a t i o n a t 0 time.  a.  Control  b.  500 m l . d i s t i l l e d  c.  1000 m l . d i s t i l l e d  d.  500 m l . sea water  e.  750 m l . sea water  f.  1000 m l . sea water  g.  750 m l . 1% x sea water  Seal  water  #1  S e a l #2  water  24  25  are o v e r t a x e d by t h e i n g e s t i o n o f s a l t water.  Does t h e  k i d n e y f u n c t i o n e f f i c i e n t l y enough t o r i d t h e body o f t h e ingested ions without  t a x i n g the r e s e r v e s o f body water?  Table I presents the t o t a l output o f f l u i d ,  c h l o r i d e , sodium  and p o t a s s i u m as a p e r c e n t a g e o f t h e t o t a l i n p u t .  The  volume o u t p u t f o l l o w i n g d i s t i l l e d water i n g e s t i o n i s from 42-79%.  When s e a water i s i n t u b a t e d , t h e amount o f water  r e q u i r e d t o e l i m i n a t e a l l o f t h e sodium and c h l o r i d e i o n s i s g r e a t e r than t h a t made a v a i l a b l e by s e a water a l o n e .  With  1% x s e a w a t e r , more than 100% o f t h e volume i n g e s t e d i s e x c r e t e d w i t h i n 13 hours, a l t h o u g h n o t a l l o f t h e sodium and c h l o r i d e i o n s a r e (94 and 63 - 80%, r e s p e c t i v e l y . ) I n a l l cases two t o f i v e times t h e amount o f p o t a s s i u m i n p u t i s e x c r e t e d w i t h i n t h e 13 hours, whereas t h e p e r c e n t o u t p u t o f the sodium and c h l o r i d e i o n s i s between 3 5 and 69% and 28 and 55%, r e s p e c t i v e l y f o r sea water experiments.  The  i n g e s t i o n o f 1% x s e a water i s found t o r e s u l t i n t h e e x c r e t i o n w i t h i n 13 hours o f 1% .to .'-12 times the i o n o u t p u t as compared t o t h e t e s t s u s i n g normal sea w a t e r . T a b l e I I l i s t s t h e o s m o t i c and i o n i c  concentrating  c a p a c i t i e s t h a t have been o b t a i n e d f o r t h e k i d n e y s o f t h e two seals studied.  S e a l #2 had h i g h e r v a l u e s f o r o s m o l a l i t y and  e l e c t r o l y t e concentrations.  The maximum o s m o l a l i t y was  a t t a i n e d i n S e a l #1 two hours a f t e r 1000 m l . o f s e a water were i n t u b a t e d , and i n S e a l #2, 13 hours a f t e r 750 ml. o f sea water were i n t u b a t e d , w i t h v a l u e s o f 1700 and 2050 mOsm./l., r e s p e c t i v e l y .  The maximum sodium i o n c o n c e n t r a t i o n  o c c u r r e d i n S e a l #1 d u r i n g t h e f i f t h hour o f t h e 1000 m l .  26  TABLE I:  P e r c e n t a g e o f i n p u t o f volume, c h l o r i d e , sodium and p o t a s s i u m e x c r e t e d i n 13 hours.  Water output (%)  S e a l #1  Chloride output (%)  Sodium output (%)  potassium output (%)  500 m l . D.W.  79  1000 ml. D.W.  55  500 m l . S.W.  73  50  63  313  750 m l . S.W.  60  49  61  205  1000 m l . S.W.  63  55  69  256  S.W. 128  80  94  380  750 m l . ±H  x  Water output S e a l #2  ( % )  Chloride output  Sodium output  (%)  (%)  Potassium output :•{%)  500 m l . D.W.  58  1000 m l . D.W.  42  500 m l . S.W.  50  41  44  549  750 m l . S.W.  48  39  49  317  1000 m l . S.W.  35  28  35  193  S.W. 13 2  63  94  335  750 m l . Ik x  Maximum v a l u e s r e c o r d e d f o r u r i n e o s m o l a l i t y  TABLE I I :  and  chloride,  sodium and potassium i o n  concentrations. O.P. Max.(mosm./l.)  U/P  S e a l #1  1700  5.07  1099  1.87  S e a l #2  2050  5.93  1099  2.25  Max.(mEq./l.)  U/P  S.W.  U/S.W.  S e a l #1  496  3.08  447  1.11  S e a l #2  523  3.02  447  1.17  U/P  S.W.  U/S.W.  Na  S.W.  U/S.W.  +  Cl Max.(mEq./l.) S e a l #1  472  3.37  448  1.05  S e a l #2  508  3.90  448  1.12  Max.(mEq./l.)  U/P  S.W.  U/S.W.  K  +  S e a l #1  172  34.4  10  17.2  S e a l #2  263  52.6  10  26.3  OPEN SEA WATER ( B a r n e s , Cl" Na K  +  : 548.30 470.20  + :  :  9.96  19 54)  28  o f sea water t e s t and i n S e a l #2 d u r i n g the f o u r t h hour o f the 750 m l . sea water t e s t , w i t h v a l u e s o f 496 and 523 mEq./l., r e s p e c t i v e l y .  Tne maximum c h l o r i d e i o n  - c o n c e n t r a t i o n was r e a c h e d i n S e a l #1 n i n e hours a f t e r i n t u b a t i o n o f 750 m l . o f 1% x sea water and i n S e a l #2 f o u r hours a f t e r i n t u b a t i o n o f 500 m l . o f sea w a t e r .  The  p o t a s s i u m v a l u e s were a t t h e i r maximum 13 hours a f t e r 500 ml. o f sea water were i n t u b a t e d i n S e a l #1 and 12 hours a f t e r t h e same i n S e a l #2. The  urine/plasma  (U/P) r a t i o s a r e p r e s e n t e d  i n Table I I .  The r a t i o s o f o s m o l a l i t y and 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 the u r i n e t o t h a t o f sea water a r e a l s o p r e s e n t e d II.  i n Table  These r a t i o s i n d i c a t e t h a t t h e c h l o r i d e and sodium  e x c r e t e d i n t h e u r i n e a r e p r e s e n t a t about the same c o n c e n t r a t i o n as i n sea w a t e r , whereas the p o t a s s i u m i o n c o n c e n t r a t i o n and o s m o l a l i t y a r e h i g h e r i n t h e u r i n e than i n sea water.  F o r comparisons, t h e i o n i c c o n c e n t r a t i o n s o f  "open" sea water a r e l i s t e d .  29 DISCUSSION  I n t e s t i n a l a b s o r p t i o n i n man and dog has been shown t o be complete w i t h i n 12 hours a f t e r f e e d i n g . ( D a v e n p o r t , 1961). A l t h o u g h t h e g a s t r o - i n t e s t i n a l p h y s i o l o g y o f the s e a l has n o t been examined and e x p e r i m e n t s t o determine t h e r a t e o f passage o f f o o d were n o t attempted, i t was assumed t h a t t h e s e a l , a c a r n i v o r e , would be i n a p o s t - a b s o r p t i v e s t a t e by 36 hours a f t e r i t s l a s t meal.  i f s o , then., changes i n t h e  plasma and u r i n e a f t e r t h i s time would be due p r i m a r i l y t o the f l u i d s i n g e s t e d and.absorbed d u r i n g t h e experiments r a t h e r than by any f o o d r e m a i n i n g i n the stomach and i n t e s t i n e . G a s t r i c e v a c u a t i o n (Hunt, et. a_l., 1951) and a b s o r p t i o n i n the s m a l l i n t e s t i n e  (Parsons and Wingate, 1961) have been  shown t o be s l o w e r f o r h y p e r t o n i c s o l u t i o n s than f o r hypo- and isotonic solutions.  Therefore, i t i s probable that  d i s t i l l e d water i s absorbed more r a p i d l y than t h e s e a water solutions.  R e t a r d e d a b s o r p t i o n o f t h e s e a water  solutions  o c c u r s a l s o because o f t h e presence o f magnesium and s u l f a t e i o n s , w h i c h a c c o r d i n g t o Davenport  (1961), "... a r e s l o w l y  absorbed, and t h e i r presence i n i n t e s t i n a l c o n t e n t s p r e v e n t s water a b s o r p t i o n . "  Changes i n plasma o s m o l a l i t y and  e l e c t r o l y t e composition r e f l e c t the absorption of intubated solutions.  I n t h i s p r o j e c t , plasma changes a f t e r  fluid  i n t u b a t i o n were apparent o n l y a f t e r t h e i n g e s t i o n o f t h e h i g h e r volumes and c o n c e n t r a t i o n s o f e l e c t r o l y t e s p o s s i b l y because o f t h e l a r g e b l o o d volume o f marine mammals as compared w i t h t e r r e s t r i a l mammals and the d i l u t i o n  effect.  30  Smirk, (1933) u s i n g human s u b j e c t s , demonstrated t h a t one l i t e r o f d i s t i l l e d water was absorbed w i t h i n 22 t o 25 m i n u t e s . Klisiecke, et al..  (1933) found t h a t a b s o r p t i o n o f d i s t i l l e d  water i n dogs took s l i g h t l y l o n g e r . likely  I t t h e r e f o r e seems  t h a t i f plasma changes o c c u r r e d , they s h o u l d be  o b s e r v e d i n t h e s e a l 1^ hours a f t e r i n t u b a t i o n . of  The absence  d i a r r h e a may i n d i c a t e complete o r near-complete a b s o r p t i o n .  Magnesium and s u l f a t e i o n s i n c o n c e n t r a t i o n s found i n sea water a r e e m e t i c s f o r humans ( F u t c h e r , e t a l . ,  1943),  a l t h o u g h they can s a f e l y i n g e s t and c o m p l e t e l y absorb s m a l l quantities  (Goodman ..and Gilman, 1965) .  These s e a l s d i d n o t  appear t o have any t r o u b l e a b s o r b i n g t h e s e i o n s s i n c e no d i a r r h e a was o b s e r v e d .  Any f e c a l m a t t e r v o i d e d was t h i c k ,  s l i m y and c h a r a c t e r i s t i c o f t h e s e a l . In a l l mammals t h e r e a r e s e v e r a l s i t e s o f f l u i d  excretion,  such as t h e eyes, nose, s a l i v a r y g l a n d s and k i d n e y s . eyes  (Thaysen and Thorn, 19 54) and s a l i v a r y g l a n d s  The  (Thaysen,  et a l . , 1954) produce f l u i d s w i t h a p o t a s s i u m i o n c o n c e n t r a t i o n t h a t i s h y p e r t o n i c t o t h e b l o o d plasma. it i s likely  that n e i t h e r these, nor  However,  t h e nose, p l a y e d a  s i g n i f i c a n t r o l e i n e x c r e t i n g excess water o r e l e c t r o l y t e s . O b s e r v a t i o n s d u r i n g e x p e r i m e n t s i n which d i s t i l l e d  water  was i n t u b a t e d i n d i c a t e d no i n c r e a s e o f f l u i d from t h e s e a r e a s , whereas i n t h e s e a water e x p e r i m e n t s , f l u i d o u t p u t from these a r e a s d e c r e a s e d .  E x t r a r e n a l s i t e s f o r water and  e l e c t r o l y t e e x c r e t i o n , comparable t o those o f marine b i r d s and r e p t i l e s , have n o t been r e p o r t e d i n mammals.  The main  31  s i t e o f o s m o t i c and i o n i c r e g u l a t i o n i n t h e harbor s e a l can, t h e r e f o r e , be viewed as o c c u r r i n g p r e d o m i n a n t l y i n t h e kidneys. The volume and c o m p o s i t i o n o f t h e body f l u i d s o f mammals a r e r e g u l a t e d w i t h i n narrow l i m i t s .  The r e g u l a t o r y  c a p a c i t i e s o f the k i d n e y can be determined by s u b j e c t i n g e x p e r i m e n t a l a n i m a l s t o such c o n d i t i o n s as d e h y d r a t i o n , h y d r a t i o n and s a l t - l o a d i n g .  The o s m o t i c and i o n i c r e g u l a t o r y  c a p a c i t i e s of the kidney r e f e r to the a b i l i t y of the kidney, as d i c t a t e d b y changes i n body f l u i d s , t o m a i n t a i n t h e q u a n t i t y and q u a l i t y o f substances which a r e u l t i m a t e l y excreted.  When body f l u i d s change i n pH, o s m o t i c p r e s s u r e ,  i o n i c c o m p o s i t i o n o r volume, mechanisms a r e i n i t i a t e d by the nervous and e n d o c r i n e systems which a c t on the r e n a l system t o r e g a i n t h e e q u i l i b r i u m s t a t e .  Changes i n k i d n e y  p r o c e s s e s , f o r t h e most p a r t , i n v o l v e a l t e r a t i o n s i n t h e r e a b s o r p t i o n and s e c r e t i o n ! . p r o c e s s e s , and a l s o i n t h e glomerular f i l t r a t i o n rate  (GFR).  Changes i n t h e GFR a r e  seldom d e t e c t e d i n man, b u t i n s e a l s they a r e f e q u e n t and e s p e c i a l l y marked a f t e r f e e d i n g ( H i a t t and H i a t t , 1942) and d u r i n g a s p h y x i a (Lowrance,  et al.,  1956).  The o v e r a l l r e s u l t  o f these p r o c e s s e s i s t h e p r o d u c t i o n o f a u r i n e v a r y i n g i n volume and c o m p o s i t i o n which r e s u l t s i n t h e maintenance o f w e l l - r e g u l a t e d body f l u i d s . P e r i o d s o f d e h y d r a t i o n (the c o n t r o l experiments)  resulted  i n r e l a t i v e l y l o w r a t e s o f u r i n e p r o d u c t i o n and e l e c t r o l y t e e x c r e t i o n (sodium and c h l o r i d e ) .  An average o f 14 t o 15 m l .  32  of u r i n e per hour was  produced by b o t h s e a l s .  s i m i l a r t o the q u a n t i t i e s determined meals by Smith  f o r p e r i o d s between  (1935), B r a d l e y and B i n g  S c h m i d t - N i e l s e n , e t a l . (1959).  Man  These were  (1942) and  produces on the average  30 m l . o f u r i n e per hour, i n cases o f moderate  hydropenia  and can drop to 12 t o 18 m l . per hour i n cases o f extreme dehydration  ( P i t t s , 1963).  D u r i n g moderate d e h y d r a t i o n  the  d e c r e a s e d u r i n a r y o u t p u t i s due t o changes i n water r e a b s o r p t i o n and not to a l t e r a t i o n s o f the GFR.  I n more  extreme d e h y d r a t i o n , the changes i n the f i l t r a t i o n r a t e a r e caused by a reduced b l o o d volume.  In the s e a l , low u r i n e  volume d u r i n g d e h y d r a t i o n and s t a r v a t i o n has been a t t r i b u t e d t o i n c r e a s e d e l e c t r o l y t e and water r e a b s o r p t i o n ( B r a d l e y , e t a l . , 1954)  and t o v a s o c o n s t r i c t i o n w i t h the r e s u l t a n t  r e d u c t i o n i n the GFR  ( H i a t t and H i a t t , 1942).  I t was  proposed by the H i a t t s t h a t the reduced u r i n e f l o w between meals e n a b l e s the s e a l to conserve i t s water s u p p l y . low u r i n e o u t p u t t h e r e was  With  a l s o a low e l e c t r o l y t e e x c r e t i o n  and a h i g h u r i n a r y o s m o t i c p r e s s u r e .  The  high  osmotic  p r e s s u r e was p r o b a b l y due t o a h i g h urea o u t p u t , w h i c h i s the major o s m o t i c a l l y a c t i v e substance fasting  (Smith, 1935).  i n the u r i n e d u r i n g  W i t h h i g h a n t i d i u r e t i c hormone  (ADH)  and a l d o s t e r o n e l e v e l s the r e s u l t i s a h i g h p e r m e a b i l i t y o f water and r e a b s o r p t i o n o f e l e c t r o l y t e s i n the nephrons and a c o n c e n t r a t e d u r i n e w i t h a h i g h o s m o t i c d u r i n g d e h y d r a t i o n and s t a r v a t i o n .  pressure  Maximum r e a b s o r p t i o n i s  a l s o a s s i s t e d by reduced GFR w h i c h decreases  filtration  33  and f i l t r a t e p e r f u s i o n i n a l l nephrons, r e s u l t i n g i n a l o n g e r p e r i o d o f c o n t a c t between f i l t r a t e and tubular c e l l s .  reabsorbing  W i t h the r e d u c t i o n o f f i l t r a t e ,  r e a b s o r p t i v e mechanisms may removing s o l u t e s .  the  o p e r a t e more e f f i c i e n t l y i n  Smith (1936) found t h a t c o n s i d e r a b l e  q u a n t i t i e s o f ammonia, c r e a t i n i n e and c r e a t i n e were a l s o p r e s e n t i n the u r i n e i n a d d i t i o n t o u r e a , 24 t o 36 hours a f t e r the l a s t meal, and c o n t r i b u t e d t o the o s m o l a l i t y . In the c o n t r o l t e s t s , u r i n e volumes were between 14  and  15 m l . per hour and the c o n c e n t r a t i o n s o f sodium and c h l o r i d e i o n s were low, i n d i c a t i n g a r e l a t i v e l y c o n s t a n t o u t p u t  of  osmotically active particles requiring a certain quantity o f water, and a l s o a near-maximum r e a b s o r p t i o n o f water and these two e l e c t r o l y t e s . the two s e a l s i n F i g u r e 2a may  The  d i f f e r e n c e s between  be a c c o u n t e d f o r by  k i d n e y s i z e s , l e v e l s o f o r g a n i c substance  The  different  excretion, urine  c o n c e n t r a t i n g a b i l i t i e s or d i f f e r e n t degrees o f b e f o r e the t e s t s .  filtered  dehydration  c o n c e n t r a t i n g a b i l i t i e s o f the  s e a l s a r e shown i n F i g u r e 2a, i n which S e a l #1  two  concentrated  i t s u r i n e to a maximum o f 1550 mOsm./l., w h e r e a s S e a l  #2  r  c o n c e n t r a t e d i t s u r i n e as h i g h as 2050 mOsm./l. potassium  Urine  i o n c o n c e n t r a t i o n s i n the c o n t r o l were r e l a t i v e l y  h i g h e r than o t h e r e l e c t r o l y t e s and were p r o b a b l y due the movement o f p o t a s s i u m  to  out o f c e l l s as a r e s u l t o f  water movement from i n t r a c e l l u l a r to e x t r a c e l l u l a r  fluids,  r e q u i r e d t o m a i n t a i n a c o n s t a n t volume o f e x t r a c e l l u l a r f l u i d during periods of dehydration.  The e f f e c t s o f s t r e s s  34  on p o t a s s i u m s e c r e t i o n ( p i t t s , 1963) and p o s s i b l e t i s s u e damage may, i n p a r t , a c c o u n t f o r t h e r e l a t i v e l y concentrations  high  of this ion.  When f l u i d s were i n t u b a t e d , t h e r e was a d i u r e s i s w i t h i n two  hours, a water d i u r e s i s w i t h d i s t i l l e d water and an  osmotic d i u r e s i s w i t h sea water.  The p a t t e r n o f u r i n e volume  changes a f t e r d i s t i l l e d water i n t u b a t i o n was s i m i l a r t o t h e e x c r e t o r y p a t t e r n i n man and dog a f t e r i n g e s t i o n o f an i s o t o n i c s o l u t i o n ( P i t t s , 1963), i n t h a t t h e i n c r e a s e i n u r i n e volume was g r a d u a l .  An a b r u p t change n o r m a l l y  occurs  i n man and dog a f t e r i n g e s t i o n o f hypotonic:.', J s o l u t i o n s . Albrecht  (1950) and B r a d l e y , e t a l . (1954) r e p o r t a d i u r e t i c  p a t t e r n f o r t h e s e a l s i m i l a r t o those o f t h e dog and man.  No  measurements were made t o determine whether t h e GFR changed d u r i n g any o f t h e t e s t s .  However, B r a d l e y , e t a l .  Page, e t a l . (1954) and S c h m i d t - N i e l s e n ,  (1954),  e t a l . (1959) found  t h a t t h e GFR d i d n o t change d u r i n g e l e c t r o l y t e and water loading.  On t h e b a s i s o f t h e i r r e s u l t s , i t seems p r o b a b l e  t h a t i f changes i n f i l t r a t i o n r a t e d i d n o t o c c u r ,  then t h e  changes i n 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 i n u r i n e volume were due t o a l t e r a t i o n s i n t h e r e a b s o r p t i v e and s e c r e t o r y processes i n the kidney.  The i n c r e a s e i n u r i n e volume  c o u l d be a t t r i b u t e d t o a d e c r e a s e d l e v e l o f a n t i d i u r e t i c hormone w h i c h would i n c r e a s e water o u t p u t .  The s e a l s may  have been d e h y d r a t e d , even though t h e y were i n f r e s h water up t o t h e time o f t h e e x p e r i m e n t and had t h e o p p o r t u n i t y t o i n c r e a s e t h e i r body w a t e r , s i n c e they r e t a i n e d from 21 t o  35  50% of the i n t u b a t e d water over 13 hours.  The reduced  t h a t o c c u r s i n the s e a l d u r i n g s t a r v a t i o n may c o n t r i b u t e d to the low water The  GFR  a l s o have  output.  i n t u b a t i o n of h y p e r t o n i c s o l u t i o n s r e s u l t e d i n an  i n c r e a s e d u r i n e volume up to 210 ml. per hour w i t h i n t h r e e hours.  The p a t t e r n s of volume change f o r sea water  h y p e r t o n i c s a l t s o l u t i o n s were s i m i l a r to those by A l b r e c h t The  and  reported  (1950) and B r a d l e y , et. a l . (1954), r e s p e c t i v e l y .  t o t a l e l e c t r o l y t e e x c r e t i o n i n the sea water experiments  i n c r e a s e d w i t h the e l e c t r o l y t e l o a d .  The  i n c r e a s e d volume  or u r i n e and 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 c o u l d be f o r by d e c r e a s e d a l d o s t e r o n e  accounted  l e v e l s d u r i n g the e a r l y stages  w h i c h would r e s u l t i n d e c r e a s e d sodium r e a b s o r p t i o n and osmotic d i u r e s i s .  an  In the l a t t e r stages of the experiments  the d e c r e a s e d e l e c t r o l y t e and u r i n e volume can be by i n c r e a s e d a l d o s t e r o n e  explained  l e v e l s w h i c h would i n c r e a s e  e l e c t r o l y t e and water r e a b s o r p t i o n .  S i m i l a r ; e f f e c t s due  to  v a r y i n g l e v e l s of a l d o s t e r o n e have been demonstrated i n the dog  (Roemmelt, e_t a l . ,  1949).  In mammals, as the u r i n e volume i n c r e a s e s , the o s m o t i c p r e s s u r e decreases i f t h e r e i s no i n c r e a s e i n e x c r e t i o n of osmotically active particles.  With a decreased u r i n e  volume, t h e r e i s an i n c r e a s e d p r o p o r t i o n of s o l u t e s i n the u r i n e and thus the o s m o l a l i t y i n c r e a s e s .  The  changes i n  o s m o t i c p r e s s u r e d u r i n g the experiments can thus, i n p a r t , be e x p l a i n e d i n terms o f u r i n e volume and the p r o p o r t i o n of 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 present.  Figure 2 presents  36  a comparison o f the s p e c i f i c g r a v i t y and o s m o t i c  pressure  v a l u e s o b t a i n e d i n the d i s t i l l e d water experiments.  I t can  be seen t h a t t h e r e i s a g r e a t s i m i l a r i t y i n the changes o c c u r r i n g i n these v a l u e s . and p o t a s s i u m  The  changes i n sodium, c h l o r i d e  i o n c o n c e n t r a t i o n discussed p r e v i o u s l y are  not g r e a t enough t o account  f o r the l a r g e change i n  o s m o l a l i t y a f t e r i n t u b a t i o n o f d i s t i l l e d water.  It is  t h e r e f o r e p r o b a b l e t h a t the amount o f t o t a l s o l i d s b e i n g the major substance, Koch, 1965)  (urea  i n the u r i n e i s the  predominant f a c t o r d e t e r m i n i n g the o s m o t i c  pressure.  S c h m i d t - N i e l s e n , et. _ a l . (1959) found t h a t the c o n c e n t r a t i o n o f urea decreased a f t e r i n f u s i o n w i t h d i s t i l l e d water the u r i n e volume i n c r e a s e d .  and  A c o r r e s p o n d i n g change between  s p e c i f i c g r a v i t y and u r i n e volume o c c u r r e d i n these experiments  also.  The o s m o t i c p r e s s u r e o f the u r i n e decreased d i s t i l l e d water e x p e r i m e n t s , hypoosmotic to the plasma.  i n the  b u t a t no time was i t The f a i l u r e o f the u r i n e t o  become hypoosmotic i n the s e a l may assuming t h a t even though t h e r e was  be accounted a decreased  f o r by electrolyte  e x c r e t i o n , the o t h e r major c o n s t i t u e n t s o f the u r i n e (urea, ammonia, c r e a t i n e and c r e a t i n i n e ) were p r e s e n t i n s u f f i c i e n t c o n c e n t r a t i o n t o m a i n t a i n the r e c o r d e d pressure.  A l s o i n f l u e n c i n g the o s m o l a l i t y was  osmotic  the g r a d u a l  i n c r e a s e i n the u r i n e volume, w i t h i n w h i c h t h e r e was  a larger  p r o p o r t i o n of 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 than t h e r e would  37  have been i f an a b r u p t i n c r e a s e had o c c u r r e d .  I f the  p a t t e r n o f water d i u r e s i s was s i m i l a r t o t h a t o b s e r v e d i n the dog ( P i t t s , 1963) then t h e p r o p o r t i o n o f p a r t i c l e s i n the u r i n e perhaps would have been low enough t o make t h e u r i n e hypoosmotic t o t h e plasma. In t h e sea water experiments,  the urine o s m o l a l i t y  v a l u e s remained r e l a t i v e l y c o n s t a n t f o r S e a l #1, b u t i n c r e a s e d f o r S e a l #2 over t h e 13 hours f o l l o w i n g i n t u b a t i o n ( F i g u r e s 2d-2g).  F i g u r e s 6d-6g and 7d-7g showed t h a t t h e c h l o r i d e  and sodium c o n c e n t r a t i o n s i n c r e a s e d r a p i d l y a f t e r 1 t o 2 hours and then remained c o n s t a n t o r d e c r e a s e d .  Therefore,  t h e r e does n o t appear t o be an o b v i o u s major c o n t r i b u t i o n t o o s m o l a l i t y by these i o n s s i n c e a l a r g e i n c r e a s e i n i o n c o n c e n t r a t i o n s h o u l d have been r e f l e c t e d by a s i m i l a r increase i n osmotic pressure.  However, i f t h e s p e c i f i c  g r a v i t i e s o f t h e u r i n e samples a r e p l o t t e d ( F i g u r e 2d-2g) and r e l a t e d t o i o n c o n c e n t r a t i o n s and u r i n e volumes, t h e osmotic pressure  t r e n d s can be e x p l a i n e d .  W i t h an i n c r e a s e  i n u r i n e volume, t h e c o n c e n t r a t i o n o f s o l i d s d e c r e a s e s , r e f l e c t e d by t h e decrease i n s p e c i f i c g r a v i t y .  as  This  statement i s b a s e d on t h e f a c t t h a t t h e time o f t h e g r e a t e s t d e c r e a s e i n s p e c i f i c g r a v i t y o c c u r s a t t h e same time as d i u r e s i s , and a l s o t h a t S e a l #1 w i t h a g r e a t e r u r i n e volume, has t h e lower s p e c i f i c g r a v i t y .  However, a t t h i s  time,  the i o n c o n c e n t r a t i o n s g r e a t l y i n c r e a s e , thus c o u n t e r a c t i n g the decrease i n o s m o t i c p r e s s u r e e x p e c t e d by a decrease i n  38  the c o n c e n t r a t i o n o f s o l i d s e x c r e t e d .  The n e t r e s u l t i s  an o s m o t i c p r e s s u r e t h a t does n o t drop, b u t i n c r e a s e s w i t h time.  This l a t t e r increase i s probably  due t o t h e f a c t t h a t  the i o n c o n c e n t r a t i o n s remain maximal o r decrease s l i g h t l y while the s p e c i f i c g r a v i t y increases.  The i n c r e a s e s i n  s p e c i f i c g r a v i t y c o u l d be due t o an i n c r e a s e d water r e a b s o r p t i o n i n t h e l a t t e r p a r t o f the e x p e r i m e n t s , r e f l e c t e d i n t h e d e c r e a s e d u r i n e volume.  as  The s p e c i f i c  g r a v i t y values a l s o provide a p o s s i b l e e x p l a n a t i o n f o r the d i f f e r e n c e s between t h e o s m o t i c p r e s s u r e v a l u e s o f t h e two s e a l s a t t h e end o f t h e e x p e r i m e n t , s i n c e t h e s p e c i f i c g r a v i t y v a l u e s a r e d i f f e r e n t i n t h e same d i r e c t i o n as t h e o s m o t i c p r e s s u r e v a l u e s , whereas t h e i o n c o n c e n t r a t i o n s a r e very  similar. The  c o n c e n t r a t i n g c a p a c i t y o f t h e k i d n e y i n d i c a t e s how  the s e a l i s a b l e t o meet i t s water r e q u i r e m e n t s ,  whether,  i n f a c t , i t can d r i n k s e a water and remove t h e e l e c t r o l y t e s w i t h o u t body d e h y d r a t i o n o r whether i t g a i n s a l l o f i t s water from i t s f o o d .  The s e a l can c o n c e n t r a t e  c h l o r i d e to approximately open s e a water  sodium and  t h e same c o n c e n t r a t i o n s found i n  (Table I I ) , t h i s i n d i c a t e s t h a t t h e s e a l  can g a i n l i t t l e o r no water by d r i n k i n g s e a w a t e r . t h i s i s t h e case, as can be seen i n T a b l e I .  In f a c t ,  In order t o  e l i m i n a t e a l l o f t h e sodium and c h l o r i d e i n t r o d u c e d w i t h sea water t h e s e a l w i l l have t o draw on body w a t e r . F u r t h e r e v i d e n c e t o i n d i c a t e t h a t t h i s s e a l cannot b e n e f i t from d r i n k i n g l a r g e volumes o f sea water i s found  39  in  the i n a b i l i t y o f the a n i m a l t o e l i m i n a t e b o t h the water  and e l e c t r o l y t e s i n sea w a t e r .  Bradley, et a l .  (1954) s t a t e  t h a t i n the p e r i o d s between meals, f i l t r a t i o n as w e l l as water and e l e c t r o l y t e e x c r e t i o n d e c r e a s e s , i n f a c t , t u b u l a r a c t i v i t y may body needs, i . e . , the  fail  "...  t o o p e r a t e i n accordance w i t h  water and s a l t r e t e n t i o n o c c u r s d e s p i t e  need t o e l i m i n a t e l o a d s imposed e x p e r i m e n t a l l y .  11  The  r e s u l t s o f the p r e s e n t e x p e r i m e n t s s u p p o r t t h i s s u g g e s t i o n in  t h a t the s e a l r e t a i n e d from 27 t o 65% o f  .the w a t e r , from  45 t o 72% o f the c h l o r i d e and from 31 t o 65% o f the sodium a f t e r t h i r t e e n hours.  The r e s u l t s suggest t h a t by c o n t i n u e d  d r i n k i n g o f sea w a t e r , the a n i m a l may become edemic i n c r e a s e i t s body e l e c t r o l y t e c o n c e n t r a t i o n t o t o x i c If may  and levels.  the a n i m a l t a k e s i n s m a l l q u a n t i t i e s o f sea w a t e r , as i t do when f e e d i n g , t h e r e would be s u f f i c i e n t  isorrheic  water p r o v i d e d , and w i t h p o s t - f e e d i n g h y p e r f i l t r a t i o n the body would be a b l e t o e x c r e t e the excess e l e c t r o l y t e s from the  sea w a t e r .  However, i f the a n i m a l i n g e s t s sea water and  does n o t f e e d , the v a s o c o n s t r i c t i o n and reduced GFR  would  cause the water and e l e c t r o l y t e s t o be r e t a i n e d i n the body. S i n c e t h i s a n i m a l spends o n e - t h i r d o f i t s time submerged (Schmidt-Nielsen, e t a l , ,  1959), d u r i n g which the GFR,water  and e l e c t r o l y t e o u t p u t , and r e s p i r a t o r y water l o s s a r e r e d u c e d , and a l s o d u r i n g w h i c h t h e r e i s l i t t l e water  loss  by e v a p o r a t i o n and i n the f e c e s , then the p o s s i b i l i t y o f body h y d r a t i o n seems j u s t as g r e a t a h a z a r d as e l e c t r o l y t e i n t o x i c a t i o n f o l l o w i n g frequent ingestion of large q u a n t i t i e s of  sea water.  40 SUMMARY  1.  The o s m o t i c and i o n i c r e g u l a t o r y c a p a c i t i e s o f t h e k i d n e y have been determined  f o r two female harbor s e a l s d u r i n g  p e r i o d s o f d e h y d r a t i o n and water and s a l t l o a d i n g .  2.  The maximum v a l u e s o b t a i n e d f o r u r i n a r y o s m o t i c p r e s s u r e , and sodium and c h l o r i d e and p o t a s s i u m i o n c o n c e n t r a t i o n s a r e 2050 mOsm./l., 523 mEq.Na /l.» 508 m E q . C l ~ / l . and +  263 mEq.K /l., r e s p e c t i v e l y . +  3.  D i s t i l l e d water i n g e s t i o n r e s u l t s i n an i n c r e a s e i n u r i n e volume and decrease i n o s m o t i c p r e s s u r e and i o n concentrations.  4.  F o l l o w i n g sea water  ingestion, a large increase i n urine  volume o c c u r s w i t h i n two hours, u r i n e o s m o l a l i t y remains c o n s t a n t o r increases', t h e sodium and c h l o r i d e i o n c o n c e n t r a t i o n s i n c r e a s e t o t h e i r maximum v a l u e s w i t h i n 3 t o 5 hours, and t h e p o t a s s i u m i o n c o n c e n t r a t i o n behaves d i f f e r e n t l y from these i o n s .  5.  The c o n c e n t r a t i o n s o f sodium and c h l o r i d e i n t h e u r i n e a r e a p p r o x i m a t e l y e q u a l t o those o f f u l l s t r e n g t h sea water, i n d i c a t i n g t h a t no water can be g a i n e d from i t s ingestion.  I n o r d e r f o r t h e s e a l t o e l i m i n a t e these  e l e c t r o l y t e s i t must draw on i t s body water.  41  LITERATURE CITED  A l b r e c h t , C a r o l y n B., 1950. T o x i c i t y o f sea water i n mammals. Amer. J . P h y s i o l . 163: 370-385. Andersen, H a r a l d T., 1966. P h s y i o l o g i c a l a d a p t a t i o n s i n d i v i n g v e r t e b r a t e s . P h y s i o l . Rev. 46: 212-243. Barnes,  H., 1954. Some t a b l e s f o r the i o n i c composition o f sea water. J . exp. B i o l . 3_1: 582-588.  Bradley, S.E. and R.J. Bing, 1942. Renal f u n c t i o n i n the harbor s e a l (phoca v i t u l i n a , L.) d u r i n g a s p h y x i a l ischemia and pyrogenic hyperemia. J . C e l l , and Comp. 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F i s h e r , 1935. The r e s p i r a t o r y metabolism o f t h e s e a l and i t s a d j u s t m e n t t o d i v i n g . J . C e l l and Comp. P h s y i o l . 2: 137-151; I r v i n g , L., K.C. F i s h e r and F.C. M c l n t o c h , 1935. The water b a l a n c e o f a marine mammal, t h e s e a l . J . C e l l , and Comp. P h y s i o l c j6: 387-391. K l i s i e k e , A., M. P i c k f o r d , P. R o t h s c h i l d and E.B. Verney, 1933. The a b s o r p t i o n and e x c r e t i o n o f water by t h e mammals. P t . 1. The r e l a t i o n between a b s o r p t i o n o f water and i t s e x c r e t i o n b y t h e i n n e r v a t e d and d e n e r v a t e d k i d n e y . P r o c . Roy. S o c , B, 112: 496-521. Koch, A., 1965. K i d n e y f u n c t i o n and body f l u i d s . I n " P h y s i o l o g y and Biophysics," 19th e d i t i o n . Eds. Ruch and P a t t o n . Saunders, P h i l a d e l p h i a pp. 843-870. L i l l y , John C , 1964. 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The e f f e c t o f osmotic g r a d i e n t s on f l u i d t r a n s f e r a c r o s s r a t i n t e s t i n e in vitro. Biochem. b i o p h y s . a c t a , 46_: 170-183. P i t t s , R.F., 1963. p h y s i o l o g y o f t h e Kidney and Body F l u i d s . Year Book M e d i c a l P u b l i s h e r s , I n c . , Chicago. Roemmelt, J . C , O.W. S a r t o r i u s and R.F. P i t t s , 1949. E x c r e t i o n and r e a b s o r p t i o n o f sodium and water i n t h e a d r e n a l e c t o m i z e d dog. Am. J . P h y s i o l . 159: 124-136.  43  S c h e f f e r , V.B., 1958. S e a l s , S e a - L i o n s and Walruses: A Review o f t h e P i n n i p e d i a . S t a n f o r d U n i v . P r e s s , Stanford, C a l i f o r n i a . S c h m i d t - N i e l s e n , B o d i l , H.V. Murdaugh, J r . , R o b e r t a O ' D e l l and J . B a c s a n y i , 19 59. Urea e x c r e t i o n and d i v i n g i n t h e s e a l (Phoca v i t u l i n a , L . ) . J . C e l l , and Comp. P h y s i o l . 53_: 393-411. S c h o l a n d e r , P.F., 19 64. A n i m a l s i n a q u a t i c environments: d i v i n g mammals and b i r d s . Handbook o f p h y s i o l o g y , S e c t . 4: A d a p t a t i o n t o t h e Environment. Amer. P h y s i o l . S o c , Wash., D.C. Smirk, F.H., 1933. The e f f e c t o f water d r i n k i n g on t h e b l o o d c o m p o s i t i o n o f human s u b j e c t s i n r e l a t i o n t o d i u r e s i s . J . P h y s i o l . £8: 127-146. Smith, H.W., 1936. The c o m p o s i t i o n o f u r i n e i n t h e s e a l . J . C e l l , and Comp. P h y s i o l . l_i 465-474. Sperber, I . , 1944. S t u d i e s on t h e mammalian k i d n e y . Z o o l o g i s k a B i d r a g F r a n U p p s a l a 22} 249-43 2. Thaysen,  J.H. and N.A.S. Thorn, 1954. E x c r e t i o n o f u r e a , sodium, p o t a s s i u m and c h l o r i d e i n human t e a r s . Amer. J . P h y i o l . 178: 160-164.  Thaysen,  J.H., N.A.S. Thorn and I . L . Schwartz, 1954. E x c r e t i o n of sodium, p o t a s s i u m , c h l o r i d e and carbon d i o x i d e i n human p a r o t i d s a l i v a . Amer. J . P h y s i o l . 178: 155-159.  

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