UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Caffeine as a hypertensive reagent Crichlow, Eugene Chinloy 1960

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1960_A6_7 C7 C2.pdf [ 3.83MB ]
Metadata
JSON: 831-1.0106103.json
JSON-LD: 831-1.0106103-ld.json
RDF/XML (Pretty): 831-1.0106103-rdf.xml
RDF/JSON: 831-1.0106103-rdf.json
Turtle: 831-1.0106103-turtle.txt
N-Triples: 831-1.0106103-rdf-ntriples.txt
Original Record: 831-1.0106103-source.json
Full Text
831-1.0106103-fulltext.txt
Citation
831-1.0106103.ris

Full Text

CAFFEINE AS A HYPERTENSIVE REAGENT by EUGENE CHINLOY CRICHLOW B.Sc., U n i v e r s i t y o f B r i t i s h Columbia, 195S,  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of BIOLOGY AND BOTANY We accept t h i s t h e s i s as conforming t o the required standard.  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , I960.  In presenting the  this  r e q u i r e m e n t s f o r an  thesis in partial  advanced degree a t the  of B r i t i s h Columbia, I agree that it  freely  agree that for  available  the  f o r r e f e r e n c e and  permission f o r extensive  s c h o l a r l y p u r p o s e s may  D e p a r t m e n t o r by  be  copying or p u b l i c a t i o n of t h i s  gain  shall  a l l o w e d w i t h o u t my  D e p a r t m e n t o f Biology and  Botany  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r S, C a n a d a . D a  te  April 25.  1960  study.  I  copying of  his representatives.  be  shall  Columbia,  the  of  University  Library  g r a n t e d by  that  not  fulfilment  make  further this  Head o f  thesis my  I t i s understood  thesis for written  financial  permission.  ii  ABSTRACT  Caffeine has been shown to induce a transient hypertensive state i n Wistar rats.  The height to which the blood pressure rises  in this caffeine-induced hypertension, and the duration of this hypertensive state was found to be dependent on the concentration of caffeine administered. Caffeine exposed to negatively ionized a i r was shown to undergo a loss i n i t s pressor activity.  This loss i n pressor activity  was found to be greater when the caffeine was exposed i n solution than when i t was exposed i n the crystalline state. Once the blood pressures of Wistar rats were elevated with injections of caffeine and had again returned to normal levels there were no further rises i n blood pressures with the administration of an equal number of injections of this drug*  iii TABLE OF CONTENTS Page I.  INTRODUCTION  1  II.  RECENT CONCEPTS OF EXPERIMENTAL HYPERTENSION  2  A.  2  B.  NEUROGENIC a. Cerebral role  2  b. Carotid sinus  3  c. Psychogenic factors  4  NEPHROGENIC  5  a. Loss of a protective action by the kidney b. Renoprival hypertension  5 7  c. Secretion of a renal pressor substance d. Initiation of renal hypertension  C.  D.  e. Validity of the renal pressor system ENDOCRINAL a. Adrenal medulla  7 8 9 10 10  b. Adrenal cortex  11  c. Salt and i t s effect on hypertension  12  d. Adrenal regenerated hypertension  13  e. Anterior pituitary  14  INTERPLAY OF SYSTEMS  14  a. Neurogenic-Nephrogenic  15  b. Nephrogenic-Endocrinal  16  APPARATUS AND METHOD IN DETERMINING BLOOD PRESSURE a. Apparatus b. Anesthesia c. Blood pressure determination ESTABLISHMENT OF CONTROL VALUES AND A CRITERION OF HYPERTENSION a. C o n t r o l values o f blood pressure b. C r i t e r i o n of hypertension EXPERIMENTAL A.  THE EFFECT OF NEGATIVELY IONIZED AIR ON THE PRESSOR ACTIVITY OF CAFFEINE a. I n t r o d u c t i o n b. Source o f n e g a t i v e l y i o n i z e d a i r EXPERIMENT I . PRESSOR ACTIVITY OF NORMAL CAFFEINE EXPERIMENT I I . PRESSOR ACTIVITY OF CAFFEINE EXPOSED IN SOLUTION TO NEGATIVELY IONIZED AIR EXPERIMENT I I I . PRESSOR ACTIVITY OF CAFFEINE EXPOSED IN THE CRYSTALLINE STATE TO NEGATIVELY IONIZED AIR  B.  DISCUSSION  C.  THE EFFECT OF THE CONCENTRATION OF CAFFEINE ON THE DEGREE OF HYPERTENSION AND THE DURATION OF THE HYPERTENSIVE STATE Introduction EXPERIMENT IV. THE HYPERTENSIVE EFFECT OF A CAFFEINE SOLUTION OF CONCENTRATION 0.1 MILLIGRAM PER MILLILITER  Page  D.  EXPERIMENT V. THE HYPERTENSIVE EFFECT OF A CAFFEINE SOLUTION OF CONCENTRATION O.Ol MILLIGRAM PER MILLILITER  38  EXPERIMENT V I . THE HYPERTENSIVE EFFECT OF A CAFFEINE SOLUTION OF CONCENTRATION 0.001 MILLIGRAM PER MILLILITER  39  DISCUSSION  40  VI.  GENERAL DISCUSSION  49  VII.  SUMMARY  52  VIII.  CONCLUSIONS  54  IX.  LITERATURE CITED  55  TABLE OF FIGURES, TABLES, and PLATES  Page Figures 1, 2, and 3.  32  Figure 4.  36  Figures 5, 6, and 7.  43  Figure 8.  47  Table 1.  20  Table 2.  23  Table 3.  33  Table 4.  34  Table 5.  35  Table 6.  44  Table 7.  45  Table 8.  46  Table 9.  48  Plate I.  19  Plate I I .  21  Plate I I I .  26  ACKNOWLEDGEMENTS  I would like to express my gratitude to, Dr. T.M.C. Taylor, Head of the Department of Biology and Botany, under whose authority this work was carried out. Dr. J . Allardyce, under whose personal direction this investigation was undertaken. Miss M. Nakashima, for her help and technical advice. Miss J.S. McKee, for proof reading this manuscript. Mrs. M. McKee, and Mrs. K. MacKenzie, for their assistance and time.  1  INTRODUCTION  The study of experimental hypertension has, within the past quarter century, progressed enormously. Although great growth has been achieved i n the knowledge of the mechanism of hypertension, most investigators know that the end i s not yet, and that hypertension w i l l not yield i t s secrets easily. As a result of the extensive work done i n the f i e l d of experimental hypertension, there have been postulated a vast number of theories as to the mechanism of the disease. These concepts may be classified, i n general, into three main categories: I Neurogenic II. Nephrogenic III Endocrinal Attention must be drawn to the fact that although these concepts may be classified into the three categories mentioned above, this has been done only to facilitate an easy approach to the study of the genesis of the disease, and that each category should not be considered as a separate entity. To describe the situation i n the words of Page (99) "We believe a more useful way to think about the problem i s i n terms of equilibrated mechanisms."  2  RECENT CONCEPTS OF EXPERIMENTAL HYPERTENSION NEUROGENIC  Within the brain there are three areas which initiate or transmit sympathetic discharges to regulate vasomotor tone. the hypothalamus, and the vasomotor center.  These are: the cortex,  The manner i n which these areas  are involved i n the production of hypertension i s not clearly understood. However i t i s evident that several influences, such as ligature of the main blood vessels to the brain ( 3 5 ) , ( l l 4 ) , intracranial pressure (37), stimulation (33)>(115),  o r  auditory  puncture of the third ventricle (142), can cause  hypertension., a. Cerebral role Schroeder (119)  has suggested four possibilities to explain the  cerebral role i n human hypertension.  However, since three of these are mere  hypotheses without any substantiating evidence, c l i n i c a l or experimental, only the fourth w i l l be considered.  He believes that the peripheral metabolic  abnormalities associated vrith hypertension may cause stimulation of cerebral metabolism. I t i s known that many primary amines, such as amphetamine, norepinepherine and serotonin, can cause central excitatory effects.  Therefore,  he states that some primary amines circulating in the blood may induce , \ M  cerebral s t i i m i l a t i o n . ^ ^ T V  T Serotonin,  c  il  if  [L  M  N  a derivative of tryptophane, has  received the greatest interest in this regard.  This primary amine occurs  i n the brain and i s believed to have a definite function in nervous tissue (17).  It has been discovered to be involved i n cerebral interneurone  transmission (119)  and apparently has a specific affinity for cortical path-  ways to the posterior and lateral hypothalamus.  3  Intravenous injections of serotonin have been reported to cause hypertension (llO).  However, Page and McCubbin have reported i t to be hypoten-  sive (lOl), and diphasic (100) (causing a f a l l followed by a slight rise i n blood pressure).  Haddy et a l (58) found that serotonin has a bidirectional  response. When small vessels are already neurogenically dilated, serotonin continues to constrict the large vessels with a net effect of constriction. However, -when the small vessels are highly constricted, serotonin dilates small vessels more than i t constricts the large vessels with a net effect of dilation. Brodie et a l (17) reported that intravenous injections of serotonin are not valid since serotonin passes the blood-brain barrier v/ith great d i f f i c u l t y . Bulle (l8) found that when serotonin was injected into the  sub-arachnoid  space i n dogs there was an elevation i n blood pressure. The use of serotonin antagonistic drugs i n the treatment of hypertension has tended to add weight to Schroeder's hypothesis that primary amines, serotonin i n particular, may induce cerebral stimulation thus causing hypertension.  Reserpine, a member of the Rauwolfia family, i s probably the  most commonly used drug i n the treatment of hypertension of a neurogenic nature. Its anti-hypertensive effects have been shown i n patients with severe as well as i n those with mild hypertension (24). Reserpine has been reported to cause mobilization and depletion of cerebral serotonin i n experimental animals (122). Its locus of action appears to be i n the posterior hypothalamus, and i t i s thought that reserpine affects the brain sites responsible for binding serotonin ( 8 l ) . b. Carotid sinus The regulatory function of the carotid sinus i n restraining excessive rises and f a l l s i n blood pressure was f i r s t clarified by Hering (66). In 1927, his demonstration of the importance of the reflex regulation of the blood pressure from the stretch receptors of the carotid sinus led him to  4 speculate on the possible role of disturbance of this reflex i n the genesis of hypertension i n man (16).  This ability of the carotid sinus receptors  in affecting the arterial blood pressure, due to stretching of the sinuses, was later confirmed by Haus et a l (60). Koch and Mies (74), and Boucket and Heymans (io) obtained experimental neurogenic hypertension by section of the sino aortic buffer nerves.  Heymans (67) obtained chronic sustained hypertension i n dogs by  ablation of the carotid sinus and aortic depressor nerves.  Crandall et a l  (25) produced hypertension i n dogs by bilateral constriction of the carotid sinus area. Wakerlin et a l (141) found that by altering cerebral hemodynamics due to reduction of volume pulse of the sinus, and of the internal and external carotid arteries, hypertension could be produced i n dogs. Hawthorne and Green (62) later confirmed this finding of Wakerlin. c. Psychogenic factors Moses et a l (93) stated that the possible origin of essential hypertension indicated that the arteriolar constriction characteristic to this disease may be due to psychogenic factors.  The site of psychic  precipitation i s believed to be the cortex and the stimuli originating there act upon the hypothalamus, which initiated excessive sympathetic discharges. Lang (83) has also suggested that essential hypertension i s initiated by disturbance of the normal regulatory (inhibitory) effect of the cerebral cortex on the hypothalamic vasomotor center. This alteration i n the cerebral cortex f i r s t produced labile and later stable elevation of blood pressure with secondary renal and cardiac involvement.  The loss i n i n i t i a l  cerebral cortical inhibition resulted from prolonged psychic stress, particularly suppressed "negative" emotions. This theory of Lang i s  5 substantiated by a considerable mass of evidence, both experimental and clinical  (123).  Goldberger (46) stated that hypertension was a sequel to continued stress.  Grollman (55) disagrees with this on the basis of lack of factual  support, and evidence which negates this (84).  NEPHROGENIC  The association of the kidney with hypertension was f i r s t suggested by Richard Bright  (16)  in  I836.  However, i t was not u n t i l  1934  that this association seemed to become more tangible when Goldblatt ( 4 4 ) succeeded i n producing hypertension i n the dog by applying a clamp to i t s renal artery.  At present there are two possibilities of the causation of  nephrogenic hypertension: (l) loss of a protective action by the kidney, and, or lack of a renal anti-pressor substance that keeps the blood pressure down, ( 2 ) secretion of a renal pressor substance, a. loss of a protective action by the kidney In 1938, Fasciolo (34) found that a rise i n blood pressure of dogs with a unilateral renal artery clamp, was transitory as long as the contralateral intact kidney was present; but on removal of the intact kidney a permanent rise in the blood pressure was obtained.  From this he deduced  that there was a "protective action by the normal kidney."  Pickering and  Prinzmetal (107) also found that i n rabbits, clamping of one renal artery produced a temporary state of hypertension with a decrease i n size of the clamped kidney and an enlargement of the normal one.  Like Fasciolo they  found that removal of the hypertrophied kidney caused permanent hypertension which they ascribed to the inability of the clamped kidney to remove some  6 substance from the blood stream. Kolff et a l (77) ureters  using dogs, implanted the  into the vena cava and found that when renal tissue was present  no hypertension developed, even though the excretory function of the kidney was thwarted by leading the urine into the blood stream. From this they concluded that hypertension was not due to the secretion of a pressor substance, nor by a substance excreted by the kidney, but to a substance produced elsewhere and normally destroyed by the kidneys. Braun Menendez (12) believed that this substance i s renotrophin, an intermediary metabolic substance which i s influenced by protein rich diets, pituitary extracts, testosterone, and thyroid hormones (13).  The  existence of hypertension i s believed by him to be due to an upset i n equilibrium between the production of renotrophin and the a b i l i t y of the kidney to cause i t s destruction, utilization, or transformation.  Increase  in the size of the normal kidney i s believed to be due to the extra effort of that kidney to remove renotrophin. Further evidence of the protective action of the normal kidney was observed by Grollman (52) who found that nephrectomy of one of a pair of rats i n parabiosis resulted i n hypertension i n that animal but not i n i t s normal partner. Moreover, i t has been observed that parabiotic union of a chronically hypertensive rat with a normal one has resulted i n a reduction i n blood pressure to normal levels of the hypertensive rat. However, when a hypertensive rat was united i n parabiosis with another hypertensive rat or with a nephrectomized  rat there was no reduction i n  blood pressure ( l 2 ) . Hamilton and Grollman (59) found that renal extracts administered to hypertensive animals and patients resulted i n a lowering of the blood pressure.  Rondell et a l ( H 3 ) have shown that a constrictor substance i n  7 the blood of completely nephrectomized rats i s present.  However, no  characterization of the substance has as yet been achieved. b. Renoprival hypertension Braun Menendez and von Euler (15) were the f i r s t to demonstrate hypertension i n rats, by complete nephrectomy. However, better success i n this f i e l d was obtained by Grollman (54) with completely  nephrectomized  dogs, by feeding the animals a low protein diet, electrolyte free diet, or by dialysing the blood by peritoneal lavage, or by the use of an a r t i f i c i a l kidney.  This type of hypertension was termed renoprival hypertension, and  i s believed to be due to an absence of a protective action of the kidney (15). Most investigators characterize renoprival hypertension as being a new type of hypertension completely different from that obtained by Goldblatt. A reduction of blood pressure i n dogs with renoprival hypertension, after vascular transplantation of a normal kidney, has been reported (92). The same results have also been reported i n humans with malignant hypertension (.9). c. Secretion of a renal pressor substance Tigerstedt and Bergman (I36) i n 1898, were the f i r s t to demonstrate that the kidney contained some substance that was capable of producing an elevation i n blood pressure.  They found that by injecting a saline extract  of rabbit kidneys into anesthetized rabbits, an elevation in blood pressure was elicited.  This active substance they named renin.  In 1938, i t was shown that kidney extracts did not contain a direct acting pressor substance as such (75) but a proteolytic enzyme (75) which was capable of initiating a series of reactions i^hich eventuallj'culminated i n an elevation of blood pressure.  This enzyme inherited the  name renin since i t was believed that this enzyme was synonomyous with the  8  substance referred to by Tigerstedt and Bergman. I t has been shown that this enzyme i s associated with the juxtaglomerular apparatus  (56).  Renin acts on a specific group of a specific alpha-2-globulin (104), renin substrate, to produce a 10 amino acid polypeptide Hypertensin I. This decapeptide had been reported to have had a pressor potency when tested i n the rat (127), but due to advances i n purification technique i t i s now considered to be vaso-inactive (22). Skeggs et a l (127) found another equally specific enzyme, "converting enzyme", which i s believed to be a metallo-protein. This enzyme, which requires chloride ions for i t s activation, acts on Hypertensin I to split off histadylleucine.  The octapeptide which results from this reaction  has been recently named Angiotensin (69),  a contraction of Angiotonin and  Hypertensin I I . Angiotensin i s now recognized as the highly vaso-active agent which i s responsible for the elevation of arterial blood pressure i n renal hypertension (63).  Page et a l (105) and R i t t e l ( i l l ) have both  been able to synthesize Angiotensin and they have found that the synthetic compound has much the same pressor activity as i t s natural analog, d. Initiation of renal hypertension The fact that hypertension could be elicited by a clamp constricting the renal artery led almost inevitably to the thought that lack of blood, or ischemia, was the immediate cause of renal hypertension. However, in experimental animals, renal ischemia has not been found necessary to e l i c i t hypertension (20),(27). Hawthorne (6l)  found that reducing femoral arterial pulse  pressure, without concurrently reducing mean pressure, caused a significant rise i n mean femoral pressure.  Kohlstaedt and Page (76)  showed that renin  was liberated from a perfused dog's kidney when pulse pressure was reduced,  9 but mean arterial pressure and renal blood flow were kept constant. Corcoran and Page (23) have suggested that a djjnunition i n pulse pressure may be the effective stimulus. However, from the data mentioned above i t seems that a reduction i n pulse pressure and not ischemia acts as a stimulus for triggering off experimental renal hypertension, e. Validity of the renal pressor system That the renal pressor system i s the operating force i n chronic experimental hypertension was established by Wakerlin (I38).  Skeggs and  Kahn (125) have found a significant increase of angiotensin i n the blood of hypertensive humans and also i n sufficient amounts i n dogs with experimental hypertension to produce hypertension i n normal dogs (126). Taquini and Fasciolo (9) have found that although the renin content of blood and of the kidneys of hypertensive patients and dogs with chronic renal hypertension was the same as i n controls of both species, clamping the renal artery caused an increase i n the renin content i n the kidney, which reached a peak 60 minutes after the initiation~of the ischemia. Braun Menendez and his group (14) have found renin i n the blood of acutely hypertensive animals and i n a few patients. Anti-renin produced by Wakerlin (139) has been shown by Goldblatt (45) to reduce blood pressure i n hypertensive dogs when the concentration of two units of anit-renin per millileter of blood was maintained.  Wakerlin  (140) found that the concentration of 14 anti-renin units per millileter of plasma was required to cause a f a l l i n blood pressure of hypertensive dogs . to their normal levels.  10 ENDOCRINAL  Except for the fact that tumours of the adrenal cortex and the adrenal medulla can cause hypertension, evidence of endocrine imbalance in the genesis of hypertension i s rather rare.  The role of the endocrine  glands appears to be secondary, conditioning, or permissive, and not primary, especially in humans. The work of Wakerlin (I38) typifies the conditioning or permissive role of the endocrine glands i n renal hypertension, a. Adrenal medulla Adrenalin i s known to increase the blood pressure, but since i t s effects are transitory i t has been thought of as having l i t t l e connection with the genesis of hypertension.  Labbe et a l (82) were the f i r s t to demon-  strate the presence of adrenalin i n benign tumours of the supra-adrenal medulla.  Beer et a l (7) believed that a vasoconstrictor substance was  present during the paroxysms of this a f f l i c t i o n , but was absent after removal of the tumour. This substance resembled adrenalin, but since the elevation of blood pressure obtained i n patients with  pheochromocytoma, the name  given to this irregularity, was not i n keeping with that produced by adrenalin, i t xvas thought that some other pressor substance was also secreted by these tumours. The dilemna was resolved by Helton (68) who discovered that the chromaffin tumours contained large excesses of nor-adrenalin i n addition to adrenalin. Barnett et a l (5) found that circulatory changes induced by infusion of nor-adrenalin into normal subjects closely resembled the phenomenon of pheochromocytoma hypertension.  I t was also found that the  subjective effects of adrenalin i<rere much greater than with the same dose of nor-adrenalin. De Langly et a l (29) have shown that when an equal mixture  11 of adrenalin and nor-adrenalin was administered to humans the effects of adrenalin predominated. The causation mechanism of this type of hypertension i s not clear, but removal of the tumour, i n general, abolishes the elevation i n blood pressure.  Green (51)  thinks that the chronic state of hypertension i n  pheochromocytoma i s mediated by a humoral mechanism and not by the development of a secondary phase of hypertension mediated through the kidneys, nor of the addition of a self perpetuating mechanism associated with vascular sclerosis.  However, Goldenberg et a l (47) believe that since  surgical removal of the tumour does not always cause a lowering of the blood pressure there i s a development of a self perpetuating mechanism as a late result of pheochromocytoma. b. Adrenal cortex Clinically, the role of the adrenal cortex i n initiating hypertension has been based on the work of Oppenheimer and Fishberg (97), and more recently that of Russi et a l (116).  These investigators found  that i n tumours of the adrenal cortex there was a relationship of the adrenal cortex to the genesis of hypertension.  Moreover, hypertension has been  recognized as one of the cardinal features in Cushing's syndrome. Selye (120), Braun Menendez ( l l ) , and Knowlton et a l (73) have shown that desoxycorticosterone (DOC), a salt retaining hormone, which i s secreted by the adrenal cortex, w i l l cause hypertension in rats when added sodium chloride i s given.  Selye (120) and Knowlton (73) both considered  that salt was necessary for the hypertension which followed the administration of DOC, since by restricting salt the hypertensive action of this compound can be prevented.  Cortisone (73) and Compound F (40), two adrenocortical  hormones, have been shown to cause an elevation in blood pressure without  12 the concurrent administration of salt* The relationship of the adrenal cortex and the administration of salt was shown by Goldman (48), who stated that salt restriction apparently induces adrenal cortical hyperactivity.  Since hypertension,,caused by the  mineralocorticoids of the adrenal cortex in the rat, i s salt dependent to a degree, i t has been suggested that salt excess acts as a primary mechanism in these hypertensive states, as in the syndrome produced in rats by severe salt excess alone (9l) and i t s possible equivalent in salt eating hypertensive American men  (26).  Hypertension caused by the adrenal cortex has been suggested to be due to electrolyte disturbance (86) and not simply to the retention of sodium and chloride.  Adrenal cortical steroids apparently act at cellular  levels to regulate the amount of sodium, potassium, and possibly magnesium within the c e l l (28),(41). DOC has been reported to increase the sensitivity of vascular smooth muscle to the pressor substances epinephrine and norepinephrine (108). c. Salt and i t s effect on hypertension Sapirestein-et a l (118) were able to produce hypertension in rats by feeding them salt in excessive quantities.  Stamler and Katz (I33)  have also shown that the excessive feeding of salt can produce hypertension in chicks. The blood pressure of hypertensive dogs, and humans has been shown to be reduced by low sodium diets (38). The sodium chloride metabolism of patients with essential hypertension has been shown to be abnormal (143). Natriuretic agents such as Chlorathiazide, which causes fluid and sodium depletion by i t s diuretic effect on the kidneys (144), and organic mercurial drugs (90) have been shown to cause a decrease in blood pressure in patients with essential hypertension (57).  13 Although the exact role which the disordered salt metabolism plays i n hypertension i s not clear, there are two possibilities postulated for i t s action: (l) narrowing of the arteriolar lumen, and (2) increasing the reactivity of arterial smooth muscle (109).  The arterial wall of  hypertensive patients and animals have been shown to contain increased amounts of sodium and water causing resistance (l37)«  swelling and thus increase peripherial  Friedman (39) has noted that the sodium concentration  gradient between the outside and the inside of the smooth muscle c e l l i s a basic determinant of tone.  An increase i n gradient of Na(outside)/  Na(inside) leads to a decrease in tone, whereas a decrease i n gradient leads to an increase i n tone.  He also noted that extracellular sodium  decreased as pressure rose and increased as pressure f e l l .  From these  findings i t can be argued that the transfer of sodium appears to be the regulator of blood pressure by regulating vascular smooth muscle tone, d. Adrenal regenerated hypertension Skelton (132)  has stimulated the interest i n the adrenal origin  of hypertension by eliciting a salt dependent hypertension during adrenal regeneration in young rats.  The mechanism i s unexplained.  I t occurred  concomittantly or as a sequel to cortical hypofunction i n which no other presently characterizable hormonal factors had been demonstrated (89)• This type of hypertension has been shown to develop after surgical enucleation of the adrenal gland when the cortex i s most rapidly regenerating, and once i t developed i t persisted u n t i l the animal died (120).  This type of  hypertension strongly resembled that produced i n the uninephrectomized salt treated rat by administration of DOC (121)  and corticosterone ( I 3 0 ) .  It has been shown to be prevented by hypophysectomy, and the presence of one intact adrenal ( l 3 l ) , also by adrenal cortical  secretory depressants such as testosterone propionate (94) and Amphenone B (21). It has been suggested that pathogenesis of this hypertensive disease might involve some functional alteration of the adrenal cortex induced by the enucleation. However, i t has also been suggested that this form of hypertension i s not mediated directly through the adrenal cortex but rather through some other mechanism which i s dependent upon the presence of an adequate degree of adrenal cortical function. Regardless of the mechanism employed i n initiating this type of hypertension i t was certain that the regenerating adrenal was an essential factor for the development of this disease (131). e. Anterior pituitary Pitt-Rivers (106) has reported to have induced hypertension i n rats by injections of large doses of crude anterior pituitary extracts, and Johnson et a l (71) have reported to have caused hypertension i n rats v/ith injections of somatotrophic hormones. Hypertension provoking properties of anterior pituitary factors, other than the syndrome evoked by ACTH (adreno-cortico-tropic hormone) are largely attributable to growth hormone supposititiously acting on a mineralocorticoid such as aldosterone which might involve the pineal (32).  INTERPLAY OF SYSTEMS  Experimental hypertension has been produced by means which involve the neural, endocrine, and renal systems. The primary mechanisms of each of these differ, secondarily however, each seems to involve the others, so that, hypertension which might have been i n i t i a l l y renal i n origin  15  becomes secondarily sustained by neural, or endocrinal.components.  The  secondary mechanisms tend to explain the persistency of some remediable types of hypertension after the removal of the primary causes, a.  Neurogenic-Nephrogenic Taquini and Fasciolo ( 1 3 4 ) found that the renin content of the  blood, and of the kidneys, of patients with hypertension and dogs with chronic hypertension due to renal ischemia was similar to that found in controls of both species. From this i t was suggested that renin plays some role during the early acute phase of hypertension in cases in which there i s an impairment of the renal circulation, but that there were serious doubts as to i t s possible participation in chronic hypertension. Ogden ( 9 5 ) suggested that a neurogenic mechanism might have taken over in the chronic stage of the renal hypertension. McCubbin et a l (87) have demonstrated that the carotid sinus and the aortic depressor mechanisms are "set" at a higher level of pressure in renal hypertensive dogs than i n normal dogs. This higher setting was shown to maintain the hypertensive state even when the initiating mechanism was removed. Kezdi (72) has also shown that i n chronic renal hypertension there was a resetting of the baroceptors in the carotid sinus at a higher level, and that this resetting of the baroceptors played a role in the maintenance of chronic renal hypertension since i t counteracted any decrease of the blood pressure below the hypertensive level. Page and McCubbin ( 1 0 2 ) found that when TEAC (tetra-ethylammonium chloride) >was administered to subjects with induced neurogenic hypertension there was a sharp and consistent f a l l in blood pressure, whereas i n those with renal hypertension there was a slight f a l l followed by a r i s e . patients with renal parenchyma lesions i t was found that TEAC, when  In  16 administered, resulted i n a depressor response as though the hypertension was primarily neurogenic i n origin, b. Nephrogenic-Endocrinal Wilson (145) stated that since adrenalectomy prevented the rise of blood pressure due to nephrectomy i n parabiotic rats, this fact together with the enhanced hypertension found by some investigators when salt was given, suggested that an excessive secretion of the adrenals may be concerned i n the chronic phase of hypertension following renal arterial constriction.  Floyer (36) believed that this influence of the adrenals  was closely linked with the control of salt metabolism. Olsen (96) noted that adrenal hypertrophy accompanied experimental nephrogenic hypertension.  Goldman et a l (48) also observed that salt restriction  apparently induced adrenal cortical hyperactivity. In rats, both renal hypertension and an injection of renin have been observed to cause hypertrophy of the zona glomerulosa of the adrenal cortex (96). Angiotensin causes sodium loss and the response to this loss may be adrenal glomerulosa hypertrophy, with a greater production of corticoids which tend to counteract the natruretic effect.  The increased  sodium retention and the production of corticoids can result i n further vascular disease and. eventually greater secretion of renin, thus initiating a vicious c i r c l e . Goldblatt (43) found that i n totally adrenalectomized dogs, constriction of the renal arteries failed to produce a rise i n blood pressure, and that adrenalectomy abolished a pre-existing hypertension i n animals maintained on a sodium diet but not given cortical extracts. Page (98) found that some rise i n blood pressure could be obtained i n such animals when cortical extracts were given. Braun Menendez (14) found  that adrenalectomy reduced the sensitivity of dogs to renin. This was attributed to a reduction of the renin substrate content of the blood. Lewis et a l (84) found that renin substrate formation was deficient i n adrenal cortical failure.  Helmer and Griffith (63) found that DOC  stimulates the formation of renin substrate i n rats.  18 APPARATUS AND METHOD IN DETERMINING BLOOD PRESSURE  a. Apparatus The blood pressure of the rats was determined by the indirect method using the capillary network i n the interdigital web of the l e f t hind leg. This leg was used as i t was the most convenient. (See pla.te I.) The apparatus used was a modification of that described by Allardyce et a l (2). (See plate II.) The mercury column described by the above mentioned workers was detached from the apparatus since accurate reproducible values of blood pressure could be obtained by using the rubber bulb alone. b. Anesthesia The anesthetic used throughout this investigation was sodium pentothal. (112).  It was prepared as a 2.5% aqueous solution according to Rixon  The weight-dose correlation described by this worker was found to  be lethal in animals between 100 and 120 grams body weight, especially when these animals were being anesthetized for the f i r s t time. Table 1 indicates the weight-dose correlation that was found most satisfactory throughout this investigation. When anesthesia was being induced for the f i r s t time i t was found that any proneness to succumb to respiratory failure could be reduced by administering a dose of the anesthetic suggested for a body weight of 10 grams below the actual weight of the animals being anesthetized. It was also found that when the suggested dose failed to produce anesthesia, provided anesthesia was not being induced for the f i r s t time, a further supplement of 0.05 to 0.10 ml. could be given without any deleterious  19  PLATE 1.  Photograph o f a p o r t i o n o f the c a p i l l a r y network i n t h e i n t e r d i g i t a l web o f W i s t a r r a t s as seen under low power. (A and B r e p r e s e n t c a p i l l a r i e s o f t h e s i z e used i n determining blood pressure).  Body weight in grams  Table 1.  Dose in cc.  Under 90  .10  90  120  •15  120  - 130  .20  130  -  145  .25  145  -  170  .30  170  -  185  .35  185. -  195  .40  195  -  250  .45 - .55  250  - 300  .55 - .70  -  Showing the dose of a 2.5$ aqueous solution  of sodium pentothal necessary to induce anesthesia in Wistar rats as determined by their body weight.  21  PLATE I I . Photograph of the apparatus used in determining the blood pressure of Wistar rats in this investigation.  22 effects. c. Blood pressure determination Blood pressure determinations were carried out i n the manner described by Allardyce et a l (2), except that whereas these workers utilized a mercury column i n addition to a rubber bulb to inflate the pressure cuff, a rubber bulb alone was employed to inflate the pressure cuff.  ESTABLISHMENT OF CONTROL VALUES AND A CRITERION OF HYPERTENSION  a. Control values of blood pressure Prior to the injections of caffeine, the blood pressures of a l l animals were taken at intervals over a period of two weeks. The average value obtained for each animal over this period was taken as the normal blood pressure value of that animal.  Table 2 shows a sample record of the blood  pressures of six Wistar rats over a period of two weeks. b. Criterion of hypertension The criterion of hypertension was taken as any elevation i n blood pressure over 20 mm. Hg above the normal blood pressure value. This arbitrary value was deduced from the variations between the average blood pressure value over a period of two weeks and the individual value at any time during this period. (See table 2.)  RAT NO.  TIME IN DAYS 1  1  110  110 104  100  110  106  110  107  2  130  128 124  120  120  130  120  125  3  120  122 120  120  126  130  124  123  4  122  122 120  126  128  122  122  123  5  110  108 112  100  110  112  110  109  6  132  130 130  132  128  130  130  130  Table 2 .  3  5  8  AVERAGE -  10  12  14  Showing the blood pressure of each of  six Wistar rats over a period of 14 days, and the average blood pressure of each animal for this period.  24  EXPERIMENTAL  THE EFFECT OF NEGATIVELY IONIZED AIR ON THE PRESSOR ACTIVITY OF CAFFEINE a. I n t r o d u c t i o n Studies on the b i o l o g i c a l e f f e c t of i o n i z e d a i r have received much a t t e n t i o n w i t h i n the l a s t decade.  I n 1955,  Kornblueh et a l (78)  found t h a t by exposing twenty seven p a t i e n t s s u f f e r i n g from hay fever, asthma, and r e l a t e d c o n d i t i o n s , to negatively i o n i z e d a i r seventeen of these reacted favourably to t h i s treatment.  This worker l a t e r reported (79)  that exposure  to n e g a t i v e l y i o n i z e d a i r e l i c i t e d favourable r e s u l t s i n persons s u f f e r i n g from hay fever, whereas exposure to p o s i t i v e l y i o n i z e d a i r r e s u l t e d e i t h e r i n no r e l i e f or i n increased d i s t r e s s . Kruger et a l (80) found that p r o t e c t i v e or l e t h a l e f f e c t s could be obtained by varying the concentration of negative or p o s i t i v e a i r ions on staphylococci. G o r r i t i and Medina (50) reported t h a t there was an average reduction of 39 mm.  Hg i n twenty four hypertensive p a t i e n t s who were  exposed to n e g a t i v e l y i o n i z e d a i r . A l l a r d y c e ( l ) , i n t h i s laboratory, found that the  hypertensive  e f f e c t of n i c o t i n e could be ameliorated i n Wistar r a t s by exposing the r a t s to negatively i o n i z e d a i r . B u t l e r ( 1 9 ) ,  also i n t h i s laboratory,  found that when Wistar r a t s were exposed t o negatively i o n i z e d a i r , caffeine-induced hypertension was much reduced. I n t r a p e r i t o n e a l i n j e c t i o n s of c a f f e i n e were found by Barker (4) to induce a hypertensive  state i n Wistar r a t s . On the basis of t h i s  worker's f i n d i n g s t h i s i n v e s t i g a t i o n was undertaken to determine the e f f e c t of negatively i o n i z e d a i r on the pressor a c t i v i t y of c a f f e i n e .  25 b. Source of negatively ionized a i r The negatively ionized a i r utilized i n this investigation was produced by a tritium ion generator by Beckett and Hicks (6) manufactured by the Wesix Electric Heater Company of California.  (See plate III.)  This apparatus employs beta radiation from tritium to ionize the a i r . Equal positive and negative ions are produced but selection of the ions of the desired charge i s accomplished by collecting the undesired ions on an electrode of opposite polarity.  By virtue of the charge on this electrode positive ions  are absorbed and negative ions are driven i n the opposite direction by electrostatic force.  Martin (88) reports that oxygen readily forms negative molecular  ions as the free electrons become attached to oxygen molecules.  However,  none of the electrons become attached to nitrogen molecules. EXPERIMENT I . PRESSOR ACTIVITY OF NORMAL CAFFEINE a. Method 100 mis. of a caffeine solution of concentration 0.1 mg. caffeine per ml. was prepared from caffeine crystals obtained from the Eastman Kodak Company, Toronto, Ontario. Six female Wistar rats were each injected intraperitoneally with 1.0 ml. of this solution on days 1 to 4 and again on days 35 to 38 inclusively. The blood pressures of these animals %irere taken at intervals over a period of 60 days. b. Results (See f i g . 1 and table 3.) On the sixth day following the administration of the f i r s t injection of caffeine the average increase in blood pressure was 68 mm. Hg above the normal average value.  This increase did not show any further rise but rather continued  to decrease until day 25 at which time the average blood pressure was again back  Photograph o f a t r i t i u m i o n g e n e r a t o r . (Used i n the p r o d u c t i o n o f n e g a t i v e l y ionized a i r ) .  27 to normal levels.  During this hypertensive state individual increases i n blood  pressure varied from 28 mm.  Hg to 106 mm.  Hg above their normal values.  There was no increase i n blood pressure following the  administration  of the second set of injections of caffeine. EXPERIMENT II. PRESSOR ACTIVITY OF CAFFEINE EXPOSED IN SOLUTION TO NEGATIVELY IONIZED AIR a. Method 100 mis. of a caffeine solution of concentration 0.1 mg. per ml. was prepared as described in experiment I.  caffeine  This volume of solution  was exposed to negatively ionized a i r for a period of 168 hours. During this period of exposure any loss i n volume due to evaporation was restored by the addition of d i s t i l l e d water to the solution. Six female Wistar rats were each injected intraperitoneally with 1.0 ml. of this "exposed" solution from day 1 to day 4 and from day 35 to day 38 with an unexposed solution of caffeine of the same concentration as that injected on days 1 to 4. The blood pressures of these animals were taken at intervals over a period of 60 days. b. Results (See f i g . 2 and table  4.)  Following the administration of the four injections of the "exposed" caffeine solution there was no appreciable rise i n the blood pressure of the animals indicative of a hypertensive state. Four subsequent injections of an unexposed caffeine solution having the same concentration as the "exposed" solution were also ineffective in e l i c i t i n g any elevation in blood pressure.  28  EXPERIMENT III. PRESSOR ACTIVITY OF CAFFEINE EXPOSED IN THE CRYSTALLINE STATE TO NEGATIVELY IONIZED AIR  a. Method Four grams of crystalline caffeine was evenly distributed on the bottom of a dry 50 ml. beaker.  The beaker and contents were placed  directly under the plastic head of the tritium.ion generator for a period of 168 hours. The caffeine was separated from the plastic head of the generator by a distance of about 4.0 cms. During the period of exposure the beaker was frequently tapped to ensure, as much as possible, complete exposure of a l l the caffeine crystals. A weight of this "exposed" caffeine necessary to make 100 mis. of a caffeine solution of concentration 0.1 mg. per ml. was dissolved i n 100 mis. of d i s t i l l e d water. 1.0 ml. of this solution was injected into each of six female Wistar rats from day 1 to day 4. From day 35 to day 38 each of these animals received daily intraperitoneal injections of 1.0 ml. of an unexposed caffeine solution of the same concentration as that administered on days 1 to 4 inclusively. The blood pressures of these animals were taken over a period of 60 days. b. Results (See f i g . 3 and table 5.) Seven days after administration of the f i r s t injection the average blood pressure of the rats rose from 129 mm. Hg to 147 mm. Hg. Although at this time there was an increase i n the average blood pressure of the animals  there were s t i l l a few animals whose blood pressures were within normal levels. On the fifteenth day, however, a l l animals were hypertensive. At this time the average increase i n the blood pressure was 42 mm. Hg above the average normal value. There was a continued decrease i n the average blood pressure from day 15 to day 27.  On day 27 the blood pressures of a l l  animals were again within normal levels.  However, this return to normal  levels was observed i n a few animals as early as day 20. Administration of the four injections of an unexposed caffeine solution of the same concentration as that prepared from the exposed crystals failed to e l i c i t any rise i n the blood pressure of the animals. DISCUSSION Figure 4 depicts in graphic form the changes in the average blood pressures of the rats after receiving intraperitoneal injections of caffeine solutions prepared from unexposed caffeine, and caffeine exposed i n the crystalline state, and i n solution, to negatiyely ionized a i r . A marked increase i n the average blood pressure was observed in those animals injected with a solution of unexposed caffeine, and also in those animals injected with a caffeine solution prepared from exposed crystals.  There was no increase i n the average blood pressure of  those animals which received injections of an exposed caffeine solution. There was a pronounced difference in the average maximum height to which the blood pressure rose i n each group of hypertensive rats.  This  average maximum height was greater i n the animals which received injections of a caffeine solution prepared from unexposed caffeine. The periods at which the peak of average maximum increase i n blood pressure was reached also showed much variance i n the two hypertensive groups.  30 In those animals which received injections of a caffeine solution prepared from unexposed caffeine, this peak of average maximum increase was attained within six days after the f i r s t injection, whereas in those animals which received injections of a caffeine solution prepared from exposed crystals, this peak occurred within fifteen days of the f i r s t injection of the solution. Irrespective of the time at which the peak of average maximum increase in blood pressure.occurred the average normal level was re-established at approximately the same time in both sets of animals. Once the rats were injected with a caffeine solution, whether the caffeine was exposed to negatively ionized a i r or not, and had regained their normal levels of blood pressure there was no further rise i n blood pressure with subsequent injections of unexposed caffeine.  This ability  of the rats to show no rise in blood pressure to subsequent injections of unexposed caffeine was observed to occur whether there was an increase in blood pressure with the f i r s t set of injections or not. The possibility that beta radiation emanating from tritium could act directly on the caffeine when i t was exposed has to be ruled out. Glasser ( 4 2 ) reported that the maximum range of beta radiation emitted from tritium i s 1.7 cms.  The distance between the tritium f o i l and the caffeine  was always greater than 4 . 0 cms. thus allowing a safety factor to insure that no direct effects of beta radiation on the caffeine were obtained. The response obtained with the animals which received injections of caffeine solutions prepared from caffeine exposed to negatively ionized air agrees, in general, with the results of Gorriti and Medina ( 5 0 ) , and with Allardyce (l) and Butler ( 1 9 ) . Although these workers obtained an antihypertensive effect by exposing their patients and animals to negatively  31 ionized a i r , i t would appear that the anti-hypertensive effect of negatively ionized air can be obtained by exposing the pressor substance as well as the rats to negatively ionized a i r . The manner in which negatively ionized air exerts an antihypertensive effect i s not fully understood. Tchijevsky (135) and Edstrom (30) reported that inhalation of the charged a i r ions triggers within the body physiological action on the cardio-vascular system. Kornblueh et a l (78) stated that negative ionization of offending airborne substances apparently diminished their allergic toxicity by changing their electric potential. F a i l l a (31) stated that chemical actions are usually facilitated by the existence of an "excited" state. This "excited" state i s often induced in molecules that have just missed being ionized and as a result of this they have considerable amounts of energy imparted to them.  Therefore  in the study of the biologic effects produced by radiation the possibility of excitation of molecules as well as ionization must be considered. The apparent complete loss of the pressor activity of caffeine exposed i n solution to negatively ionized air as compared with the partial loss of the pressor activity of caffeine exposed i n the crystalline state, i s probably due to the degree of interaction between the negatively ionized a i r and the molecules of caffeine in these two phases. Molecules i n solution tend to be more widely dispersed than molecules in a crystalline l a t t i c e .  Therefore molecules of caffeine in  solution w i l l , of necessity, afford a greater degree of interaction with negatively ionized air than molecules of caffeine which are compactly integrated i n a crystalline l a t t i c e .  Fig. 1  The changes i n the average blood pressure of six female Wistar rats after receiving four injections of .10 mg. caffeine on days 1, 2, 3 and k, and again on days 35, 36, 37 and 38.  Fig. 2 The changes i n the average blood pressure of six female Wistar rats after receiving injections, on days 1, 2, 3 and i+, of .10 mg. caffeine previously exposed i n solution to negatively ionized air for 168 hours, and injections of .10 mg. unexposed caffeine on days 35, 36, 37 and 38.  Fig. 3 The changes in the average blood pressure of six female Wistar rats after receiving injections, on days 1, 2, 3 and l+, of .10 mg. caffeine previously exposed in the crystalline state to negatively ionized a i r for 168 hours, and injections of .10 mg. unexposed caffeine on days 35, 36, 37 and 38.  32  2 2 0  6 0  140  RAT NO.  TIME IN DAYS  0 1—4  2  116  3  122  4  138  5  131  6  146  Table 3.  10  12  168 184 210  19 25  29  33 35-3S  160 132 140  130  182 164  210  170 130  124  120  N.R. 160  150  170 140  120  124  130 I30 140  138  190  244 150  240 190 210  124 140  134 130  184 168 110 142  148 150  164  4 injections of unexposed caffeine of cone. 0.1 mg«/mU  130  4 injections of unexposed caffeine of cone. 0.1 mg./ml.  1  -6  38 46  56  60  132 140  130  132  134 124  134 120  128 124  128 120  142 136 140 131 140  134 130  144 150  154 147  Showing the blood pressures of six female Wistar rats after  receiving four injections each of a caffeine solution of concentration 0.1 mg./ml., prepared from caffeine unexposed to negatively ionized air, and four subsequent injections of the same concentration 35 days after administration of the f i r s t injection.  138  1  135  2  135  3 134 4  130  5  130  6  112  1-4  • 00 Cfl CO CD CD  4  10  20  135  135  145  140 150  131  131  130  128 125  27  32  134 136 130 136 130 140  130 132  130 130  130  130  150  146 142  112  112  110  110 120  35-38 4 injections of unexposed caffeine of cone. 0.1 mg./ml.  0  4 injections of ex] caffeine (soln. ex] of cone. 0.1 nig./mi  RAT NO.  TIME IN DAYS 44 150  56  60  135 124  130  50  133 N.R. 138 133 142  142 120  138  130 130 129  134  130  140 119  137  I32  120 120  118  Table 4. Showing the blood pressures of six female Wistar rats after receiving four injections each of a caffeine solution of concentration 0.1 mg./ml., prepared from a caffeine solution exposed to negatively ionized a i r for 168 hours, and four subsequent injections of an unexposed caffeine solution of the same concentration 35 days after the f i r s t injection of the exposed solution.  TIME IN DAYS •  130  5  134  H 0 0 . •* 3 M  CO  to  138  155  27  30  130  125  128  (U  160  160  150  123 130  Table 5.  exposed Ls of co  128  50  130  132  128 128  130  128  130 130  55  C_J.  B"8 CD  C+  0  8  H-  131  3 CO 0 0j 30 H  128  130  I30 130  172  134  130 130  I32  128  127  130  151  180  187  139 126  136  130  134  134  129  187  139  127  128  132  129  128  174  161  1 1  6  60  44  130 128  138  c+- 0 (U Hj  3 0 •  35-3S  128  Hj  unexposed 0.1 mg  4  3  20  i.  3  127  Hj  15  r»o •Pf\  129  O 0 4> , p>  jecti eine  2  129  7  4 in,  1  0 1-4  Shov/ing the blood pressures of six female Wistar rats  after receiving four injections each of a caffeine solution of concentration 0.1 mg./ml..prepared from caffeine crystals exposed to negatively ionized air for 168 hours, and four subsequent injections of an unexposed caffeine solution of the same concentration 35 days after the f i r s t injection of the exposed solution.  Changes in the average blood pressure of female Wistar rats with unexposed caffeine, and caffeine exposed in solution, and i n the crystalline state, to negatively ionized a i r .  Changes in six female injections on days 1, 35,  1  36, 37  the average blood pressure of Wistar rats after receiving of *10 mg. unexposed caffeine 2 , 3 and 4 , and again on days and 3 8 .  Changes i n the average blood pressure of six female Wistar rats after receiving injections on days 1, 2 , 3 and 4 , of .10 mg. caffeine previously exposed in solution to negatively ionized a i r for 168 hours, and injections of .10 mg. unexposed caffeine on days 3 5 , 3 & , 3 7 and 3 8 .  Changes in the average blood pressure of six female Wistar rats after receiving injections, on days 1, 2 , 3 and 4 , of .10 mg. caffeine previously exposed i n the crystalline state to negatively ionized a i r for 168 hours, and injections of .10 mg. unexposed caffeine on days 3 5 , 3 6 , 3 7 and 3 8 .  37  THE EFFECT OF THE CONCENTRATION OF CAFFEINE ON THE DEGREE AND DURATION OF CAFFEINE-INDUCED HYPERTENSION  Introduction The ability of caffeine to cause an increase i n blood pressure was reported by Grollman (53) i n 1930, and later by Horst et a l ( 7 0 ) . These workers found that when caffeine was administered to humans there resulted an increase i n blood pressure concomitant with an increase i n pulse rate. Barker (4), i n this laboratory, found that when Wistar rats were injected intraperitoneally with a caffeine solution there was initiated a transient hypertensive state i n these animals. This investigation was undertaken to determine whether there existed a correlation between the degree, and duration of this caffeineinduced hypertension and the concentration of caffeine administered.  EXPERIMENT IV. THE HYPERTENSIVE EFFECT OF A CAFFEINE SOLUTION OF CONCENTRATION 0 . 1 MILLIGRAM PER MILLILITER.  a. Method 100 mis. of a caffeine solution of concentration 0.1 mg. per ml. was prepared from caffeine crystals obtained from Eastman Kodak Company, Toronto, Ontario. Four female Wistar rats and four male Wistar rats were each injected intraperitoneally with 1.0 ml. of this solution from day 1 to day 4 inclusively and again from day 49 to day 52. The blood pressures of these animals were taken at intervals over  38 a period of eighty days. b. Results (See f i g . 5 and table 6.) An immediate rise i n the average blood pressure was observed within five days of the administration of the f i r s t injection of caffeine.  This  rise continued to increase until day 20 at which time the average blood pressure was 90 mm.  Hg above the normal average value.  F om day 20 there was a consistent decrease i n blood pressure r  until day 34.  At this time the average blood pressure was again back to  normal levels. During this period of hypertension individual elevations of blood pressure were observed to vary from 26 mm. Hg to 128 mm. Hg above their normal values. There were no significant differences i n blood pressure values between the two sexes. Administration of the second set of injections failed to e l i c i t any further rise in the blood pressure of the rats.  EXPERIMENT V. THE HYPERTENSIVE EFFECT OF A CAFFEINE SOLUTION OF CONCENTRATION 0.01 MILLIGRAM PER MILLILITER  a. Method 100 mis. of a caffeine solution of concentration 0.01 mg. per ml. was prepared as described i n experiment IV. Each of four female Wistar rats and four male Wistar rats was injected intraperitoneally with 1.0 ml. of this solution from day 1 to day 4 and again from day 49 to day 52. The blood pressures of these animals were taken at intervals over  39 a period of eighty days. b. Results (See f i g . 6 and table 7.) An increase i n the average blood pressure was found within seven days of the administration of the f i r s t injection of the caffeine solution.  There was a continued increase until a maximum average value  of 63 mm. Hg above the normal value was attained on day IS. Following the attainment of this maximum increase there was a consistent decrease i n blood pressure u n t i l the normal average value was again established. This occurred on day 28. Individual variations i n blood pressure values during this hypertensive state ranged from 22 mm. Hg to 16 mm. Hg above the normal values. The only difference noted between the two sexes during this hypertensive state was the early re-establishment of the normal blood pressure of a l l the female rats on day 23 whereas this did not occur i n the males until day 28. No elevation i n blood pressure resulted from the administration of the second set of injections of caffeine.  EXPERIMENT VI. THE HYPERTENSIVE EFFECT OF A CAFFEINE SOLUTION OF CONCENTRATION 6.001 MILLIGRAM PER MILLILITER  a. Method 100 mis. of a caffeine solution of concentration 0.001 mg. per ml. was prepared as described i n experiment IV. Four female Wistar rats and four male Wistar rats were each injected intraperitoneal^ with 1.0 ml. of this solution daily from day 1  40 to day 4 and again from day 49 to day 52> The blood pressures of these animals were taken at intervals over a period of eighty days, b. Results (See f i g . 7 and table 8.) The average blood pressure was observed to increase within six days of the administration of the f i r s t injection of the caffeine solution, on day 11 the average blood pressure had attained a maximum value of 47 mm. Hg above the normal, average value. Following the attainment of this maximum increase i n the average blood pressure there was an ensuing decrease which terminated at the re-establishment of the average normal value.on day 21. Variations of 20 mm. Hg to 70 mm. Hg above the normal values of blood pressure were observed i n individual animals. There were no significant differences i n the degree or duration of hypertension between the two sexes. Administration of the second set of injections did not produce any rise i n the blood pressure of the animals. DISCUSSION Figure 8 depicts the changes i n the average blood pressure of Wistar rats after receiving injections of three different concentrations of caffeine.  Table 9 shows the differences found i n the hypertensive  state induced by each of these concentrations. There was a marked increase i n the average blood pressure with each of the concentrations used. This increase was greatest with the 0.1 mg./ml. and least with the 0.001 mg./ml., the .01 mg./ml. being intermediate. The average maximum increase in blood pressure varied with each  41 of the concentrations  used. There was a maximum increase of 90 mm.  Hg  above the normal average value i n those animals which received injections of the 0.1 mg./ml. solution, whereas with the 0.01 mg./ml. solution and the 0.001 mg./ml. solution this value was 63 mm. Hg and 47 mm.  Hg  respectively. The times at which the maximum increase in the. average blood pressure occurred were different with each of the concentrations of caffeine.  This increase occurred within 20 days of the administration of  the f i r s t injection of the 0.1 mg./ml. solution, whereas with the 0.01 mg./ml. solution this occurred within 18 days, and with the 0.001 mg./ml. solution within 11 days. During the hypertensive state induced by each of the concentrations of caffeine there were no significant differences i n the degree or duration of hypertension between the two sexes to warrant any consideration i n the differences i n response. Animals which were once rendered hypertensive by injections of caffeine and had re-established their normal levels of blood pressure did not show any increase i n blood pressure to a subsequent treatment of an equal number of injections of caffeine.  The concentration of caffeine  used i n the second set of injections was the same as that used i n the f i r s t set of injections. The response obtained with the different concentrations of caffeine parallels the results obtained by Grollman (53). This worker found that low concentrations of caffeine did not affect the blood pressure of humans whereas greater concentrations elicited an increase i n their blood pressures. The action of caffeine on the cardio-vascular system i s unpredictable since i t i s believed that this drug e l i c i t s a diphasic action,  42 a central vasoconstriction together with a peripheral vasodilation (146). Caffeine has been shown to be a central nervous system stimulant. Its action has been confined to the cerebral cortex, the medulla oblongata, and i n very concentrated doses the spinal cord (49).  In the medulla i t s  action i s specifically concerned with the vagal center, the respiratory center, and the vasomotor center.  In addition to i t s action on the central  nervous system caffeine has been shown to stimulate the myocardium of the heart thus causing an increase i n cardiac output  (49).  The increase i n blood pressure after administration of caffeine has been attributed to numerous factors.  I t has been suggested that the  increase i n blood pressure may be due to the combination of increased cardiac output due to stimulation of the myocardium of the heart together with the increasedvasomotor  tone which results from stimulation of the  vasomotor center i n the medulla  (49).  Salter (117) has also suggested that the increase i n blood pressure may be due to the initiation of a nervous state which causes an increase i n heart rate. Irrespective of the mechanisms involved i n the initiation of a hypertensive state through the administration of caffeine i t appears that this hypertensive state when induced i n Wistar rats i s dependent on the concentration of caffeine administered.  Fig. 5  The changes i n the average blood pressure of four female Wistar rats and four male Wistar rats after receiving four injections of .100 mg. caffeine on days 1, 2, 3 and 4, and again on days 49, 50, 51 and 52.  Fig. 6  The changes i n the average blood pressure of four female Wistar rats and four male Wistar rats after receiving four injections of .010 mg. caffeine on days.1, 2, 3 and 4, and again on days 49, 50, 51 and 52.  Fig. 7  The changes i n the average blood pressure of four female Wistar rats and four male Wistar rats after receiving four injections of .001 mg..caffeine on days 1, 2, 3 and 4> and again on days 49, 50, 51 and 52.  220  13  I  I8CH  2 5  CL-  140  OD  IOO 20 FIG. 5  4 0  60  80  60  80  DAYS  220  i  o  180  I  2 5  CLOD  180  FIG. 7  NO  O-  o CM NO  CV tf\  1  o -4O  -4CO  a H  cv -*  -4  11 EH  rcv  o  cv  H  rH  UN cv  CC H rH  cv cv  - * CV rH  to  rH rH  CV  NO  rH  rH  rH  rH  CV H  rH rH  O CV H  CO CV rH  NO rH rH  NO CV rH  O  o  vO  -4  O  O  O O  o cv  rH rH  CV rH  O rH rH  CV  CV  H  rH  (T\  P\ rH  O  CV H  cv cv  rH  CV  cv  rH  -4  CV rH  cn  rH  H  cv  rH  cv  ON,  rH  -4 cv  rH  to  rH rH  CN-  cv  rH rH CV rH CV CV rH  4 injections o f a caffeine solution o f concentration 0.1 mg./ml. sO  rH H  to  rH rH  o  O  NO  o  H  cv  Os OA  H  rH  H  O - * rH  rH  rH  -4;  rH  H  rH  CV  CN  ON.  cv  -* H  rH  o,  O CV rH  CV CV rH  o  CV  CO  CV H  H  rH  rH CV rH  O CV  O  IT\  O  o  CV  O rH  rH rH  -i-  O  CV  O  cv  H  CV  o  o  rH  cv  O NO rH  cn w\  H  lA  CV CV  v\ o cv  • •  ir\ £> H if\ NO rH  O  to to H  H  C"\  rH  to ON, rH  ON C«N, H  -4 rH H  H cn rH  NO ON rH  CT\  rH  cv  rH  cv cv  H  ir\  Lf\ CV rH  ON rH H  rH H  NO rH rH  o -4  to CN,  o  O  H  CV  rH  CN-  t>  rH  o -4"  NO rH  NO H  O NO rH  H  o  H  rH  ITS  rH  -i4 j 4 injections o f a caffeine solution rH concentration 0.1 mg./ml. o f O  RAT NO. SEX  rH rH  vO rH rH  rH  OrH rH  H  CV  m  -4  MALES  cv cv  H  v\ cv  cv  rH  ON CV H  rH  H  CV  C«N,  FEMALES  CV CV H  •4-  1 RAT NO.  to  0  2  111  3  120  4  110  1  116  2  122  3  126  4  125  Table 7.  1  !  ! 1 r TIME IN DAYS  |  I I  38  46  113  126 120  124  172  121  124 123  127  121 178  166  124  127 125  120  142  166 175  164  126  113 110  120  140  144 192  124  116  114 118  119  144  154 194  110  128  130 116  130  150  154 180  120  120  120 130  126  164  172 190  120  128  130 118  120  18  23  28  169 173  164  N.R. 116 173 123  7 172  13  33  49-52 4 injections of a caffeine solution of concentration 0.01 mg./ml.  FEMALES  120  1-4 4 injections of a caffeine solution of concentration 0.01 mg./m]..  MALES  1  !  1  i  58  i  i  i  64  69  74  80  119 122  127  125  125  116 113  104  116  120  120 120  119  127  120  112 115  120  120  125  120 120  118  114  118  126 131  120  120  125  130 126  131  120  130  130 120  120  126  123  Showing the blood pressures of four female Wistar rats and four male Wistar rats  after receiving four injections each, of a caffeine solution of concentration 0.01 mg./ml. and four subsequent injections of the same concentration 49 days after administration of the f i r s t injection.  RAT NO.  n  TIME IN DAYS  0  2  120  3  112  4  120  1  130  2  122  3  119  4  125  6  11  15  21  25  32  39  46  130  166  155  130  I30  126  131  130  143  164  130  132  133  120 120  125  142 166  182  130  135  120 118 120  160  158  125  130  122  190 194  125  120 124 128  162  172  158  131  159 160  140  120 120  121 125 128  174 168  155  125 125  I3I  I32  132  121  121 128 134  134  120 118  128 128  49-52 4 injections of a caffeine solution of concentration 0.001 mg./ml.  FEMALES  126  4 injections of a caffeine solution of concentration 0.001 mg./ml.  MALES  1  1—4  59  69  80  75  130  128  130  124  128  130  128  126  118  114  120 120  130  132  124 128  132  I38  127  121  119  128 120  130  121  127 128  128  125  120  132  133  Table 8. Showing the blood pressures of four female Wistar rats and four male Wistar rats after receiving four injections each of a caffeine solution of concentration 0 . 0 0 1 mg./ml. and four subsequent injections of the same concentration 4 9 days after the administration of the f i r s t injection.  Fig. 8  Changes i n the average blood pressure of Wistar rats with three different concentrations of caffeine.  Changes i n the average blood pressure of four female, and four male Wistar rats after receiving injections of .100 mg. caffeine on days 1, 2, 3 and L\, and again on days 49, 50, 51 and 52.  Changes i n the average blood pressure of four female and four male Wistar rats after receiving injections of .010 mg. caffeine on days 1, 2, 3 and 4, and again on days 49, 50, 51 and 52.  A—-—A  Changes i n the average blood pressure of four female and four male Wistar rats after receiving injections of .001 mg. caffeine on days 1, 2, 3 and 4> and again on days 49, 50, 51 and 52.  47  Concentration of caffeine used  Max. increase in blood pressure above normal average blood pressure  Time at which max. increase i n blood pressure occurred  Duration of hypertension  Max. individual increase i n blood pressure above normal blood pressure  0.100 mg./ml.  90 mm. Hg  Day 20  34 days  128 mm. Hg  0.010 mg./ml.  63 mm. Hg  Day 18  28 days  -76 mm. Hg  0.001 mg./ml.  47 mm. S  Day 11  21 days  70 mm. Hg  H  Table 9. Showing the differences in the hypertensive state induced with three different concentrations of caffeine.  49  GENERAL DISCUSSION From the results obtained in this investigation i t would appear that caffeine exposed to negatively ionized air tends to lose, i t s pressor activity.  Also that in Wistar rats the degree and duration of caffeine-  induced hypertension were dependent on the concentration of caffeine administered. It was also observed that once Wistar rats, had been injected with caffeine and had re-established their normal levels of blood pressure subsequent administration.of  an equal number of injections of caffeine of the same  concentration seemed to have no effect i n causing a further rise i n blood pressure. Beutner ($) stated that every pharmacological action was  ultimately  due to a physical change which the drug brought about in the living tissue. Moreover, the electrical potential differences in tissue were, of v i t a l function and thus by changing the potential differences existing inside the tissue by introducing certain substances into the tissue some change was initiated which resulted in the stimulation of the tissue. This worker found that certain alkaloids had the ability to change the electromotive force of an a r t i f i c i a l cell-system.  Of the  alkaloids found to possess this ability, caffeine was found to have an ability which depended on the concentration of caffeine used. The higher the concentration of caffeine used the greater was the change i n the electromotive force. I f Beutner*s cell-system can be taken as representative  of the  tissue i n vivo then an explanation of the action of caffeine as found i n this investigation can be attempted. Since negatively ionized a i r was found to depress the hypertensive effect of caffeine this loss i n the pressor activity of this drug i s  50  probably due to some interaction between negatively ionized a i r and the molecules of caffeine.  Caffeine i s a xanthine derivative, therefore  molecules of caffeine, i n solution, would be expected to possess a net positive charge due to the presence of the imidasolyl group i n the molecule. This ability of caffeine to possess a net positive charge i s probably the basis of Sjostrom and Nyakanen's report on the ability to seperate caffeine from phenacetin and antipyrine through the use of a resin column of ferric ions (124). Caffeine molecules appear to possess a net positive charge and molecules of negatively ionized a i r carry a net negative charge.  Any  interaction between these two species of molecules w i l l be one i n which there i s neutralization of the charges. Whether this results through the donation of an electron from the molecule of negatively ionized a i r to the positively charged caffeine molecule, or whether there i s fusion of the two molecules through electrostatic attraction i s unknown. However, regardless of the mechanism employed i n the interaction between these two species of molecules the loss of the net positive charge on the caffeine molecule probably affects the a b i l i t y of this substance to change the electromotive force of the tissues i n the body, thereby resulting i n the failtire of exposed caffeine to induce a hypertensive state. The tendency of the degree and duration of caffeine-induced hypertension to be reduced with decreasing concentrations of caffeine i s probably due to the inability of low concentrations to cause a large change in the electromotive force of the tissue responsible for producing hypertension. The change i n the electromotive force due to a low concentration of caffeine although strong enough to cause an increase i n blood pressure i s not strong enough to prolong or intensify this increase.  On the other hand the change  51 obtained by a higher concentration might be strong enough to induce hypertension as well as to prolong and intensify this hypertensive state. The manner i n which Wistar rats,, which have been rendered hypertensive with caffeine and have again re-established their normal blood pressure values,develop a negative response to subsequent administration of caffeine i s s t i l l not f u l l y understood.  However, i t can be suggested that  since caffeine i s reported to have a central vasoconstriction together with a peripheral vasodilatation this negative response might be due to the predominance of one of these actions over that of the other. The hypertensive effect obtained with the i n i t i a l injection of caffeine might be due to a predominance of central vasoconstriction over peripheral vasodilatation.  With subsequent injections of caffeine this  predominance i s probably altered so that peripheral vasodilatation overcomes any increase i n blood pressure that might have arisen from central vasoconstriction.  On the other hand subsequent injections of caffeine  might have facilitated peripheral vasodilatation to the degree at which the increase i n vasodilatation balances the effect of central vasoconstriction.  52  SUMMARY Caffeine exposed to negatively ionized a i r for a period of 168 hours was observed to undergo some change which resulted in a loss of i t s pressor activity i n Wistar rats. A complete loss i n pressor activity was found when the caffeine was exposed i n solution to the negatively ionized air, whereas when the caffeine was exposed i n the crystalline state there was only a partial loss in pressor activity. Animals which were once rendered hypertensive by an unexposed caffeine solution and by a caffeine solution prepared from caffeine crystals exposed to negatively ionized air, did not show any further increase i n blood pressure with a subsequent treatment of an equal number of injections of unexposed caffeine of the same concentration. This subsequent treatment was ; administered after the animals had regained their normal levels of blood pressure.  This negative response was also observed i n animals which  had not become hypertensive with injections of a caffeine solution which was exposed as such to negatively ionized a i r . The degree and duration of caffeine-induced hypertension i n Wistar rats were found to be dependent on the concentration of caffeine administered. With four 1.0 ml. injections of a 0.1 mg./ml. solution the hypertensive state lasted for 34 days, and the maximum increase i n blood pressure above the normal average value was 90 mm. Hg. With equal injections of a 0.01 mg./ml. solution the duration of the hypertensive state was 28 days and the raajcijiium increase i n blood pressure was 63 mm. Hg above the normal average value.  A similar treatment using a 0.001 mg./ml. solution produced a  .hypertensive state which lasted for 21 days and the maximum increase during this period was 47 mm. Hg above the normal average level of blood pressure.  53 There were no significant differences i n the hypertensive states of male and female rats with the concentrations of caffeine used. When once the hypertensive states were overcome and the animals had regained their normal levels of blood pressure an equal number of injections of caffeine of the same concentration as was i n i t i a l l y administered failed to produce any further increase i n the blood pressures.  iCONCLUSIONS 1.  Small intraperitoneal injections of caffeine w i l l cause a transient state of hypertension i n Wistar r a t s .  8.  In caffeine-induced hypertension the height to which the blood pressure i s elevated and the duration o f the hypertensive state, are both dependent on the concentration of caffeine administered.  3.  Wistar rats when once injected i n t r a p e r i t o n e a l l y with caffeine do not show any response i n the elevation of blood pressure with subsequent i n j e c t i o n s of caffeine of the same concentration.  4.  Negatively ionized a i r tends to have a marked e f f e c t i n decreasing the pressor a c t i v i t y of caffeine i n Wistar r a t s .  5.  Caffeine exposed i n solution to negatively ionized a i r tends to lose more of i t s pressor a c t i v i t y than caffeine exposed i n the crystalline  state.  55  LITERATURE CITED  1  Allardyce, J., unpublished data.  2  Allardyce, J., et a l , Trans. Royal Soc. Canada., 42:25, 1948.  3  Albert, D.G., et a l , C i r c , 17:761, 1958.  4  Barker, R., M.A. Thesis. University of British Columbia, 1953.  5  Barnett, A.J., et a l , Clin. Sci., 9:151, 1950.  6  Beckett, J.C., Hicks, W.W.,  7  Beer, E., et a l , Ann. Surg., 106:85, 1937.  8  Beutner, R., Jour. Pharm. and Exper. Therap., 31:305, 1927.  9  Blaquier, P., Fed. P r o c , 17:16, 1958.  10 11  Patent Application Serial # 640-434.  Boucket, J.J., Heymans, C , Compt. rend. Soc. BioL, Paris, 117:252 1934 cited Perspectives in Bio. and Med. 11(3):354, 1959. Braun Menedez, E., Hypertension, a Symposium, Bell, E.T., Minneapolis Univ., Minnesota Press, 1951. pp. 133-146.  12  Braun Menedez, E., Stan. Med. Bull., 10:65, 1952.  13  Braun Menedez, E., C i r c , 17:696, 1958.  14  Braun Menedez, E., et a l , Renal Hypertension. Springfield, 111., C.C. Thomas, 1946.  15  Braun Menedez, E., Von Euler, U.S., Nature, 160:905, 1947.  16  Bright, R., Guy's Hosp. Rep., 1:380, I836.  17  Brodie, B.B., et a l , Science, 122:968, 1955.  18  Bulle, P.H., Amer. J. of Med. Sci., 234 329, 1957.  19  Butler, R.K., unpublished data.  20  Castleman, B., Smithwick, R.H., New Eng. Jour. Med., 239:732, 1948.  21  Chappel, C.I., et a l , Endoc, 62:30, 1958.  22  Corcoran, A.C, Canad. Med. Assn. Jotir., 81:145, 1959.  23  Corcoran, A.C., Page, I.H., Am. J . Physiol., 135:361, 1942.  :  56 1954.  24  Corcoran, A.C., Am. Jour. Med.,  25  Crandall, E.E., et a l , Circ. Res.,  26  Dahl, L.K., Am. J . Clin. Nutrition, 6:1, 1958.  27  Daniel, P.M. et a l , B r i t . J . Surg., 42:2, 1954.  28  Davis, A.K., et a l , Am. J . Physiol., 166:493, 1951.  29  De Langly, C , et a l , Clin. Sci., 9:71, 1950.  30  Edstrom, G., Acta. Med. Scand., supp., 61:1-83, 1935.  31  F a i l l a , G., Medical Physics, Vol. I, 637-641, Year Book. Publishers, Inc., Chicago, 1944.  32  Farrell, G., et a l , Fed. P r o c , pt. 1, 18:44, 1 9 5 9 .  33  Farris, E.J., et a l , Am. J . Physiol., 1 4 4 : 3 3 1 , 1945.  34  Fasciolo, J.C., Rev. Soc. Argent. Biol., 14:15, 1938 cited C i r c , 17:719, 1958.  35  Fishback, H.R.,  36  Floyer, M.A.,  37  Freeman, N.E., Jeffers, W.J., Am. J . Physiol., 1 2 8 : 6 6 2 , 1940.  38  Frieden, J . et a l , Am. J . Physiol., 168:500, 1952.  39  Friedman, S.M.,  et a l , Circ. Res., 7:44, 1 9 5 9 .  40  Friedman, S.M.,  et a l , Endoc, 53 633, 1953.  41  Gaudino, M., Levitt, M.F., J . Clin. Invest., 28:1487, 1949.  42  Glasser, 0., Medical Physics, Chicago, Year Book. Publishers, Inc.,  17:383,  5:683,  1957.  et a l , J . Lab. Clin. Med., 28:1187, 1943.  Clin. Sci., 14:163, 1955.  ;  1944, 644. 43  Goldblatt, H., Ann. Inter. Med., 11:69, 1937.  44  Goldblatt, H., et a l , J . Exper. Med., 59, 1934.  45  Goldblatt, H., C i r c , 17:642, 1958.  46  Goldberger, E., Am. J . Cardiol., 1:154, 1958.  47  Goldenberg, M., et a l , Arch. Inter. Med., 86:823, 1950.  48  Goldman, E., et a l , E d o c , 38:57, 1956. n  57 49  Goodman, L., Gilman, A., The Pharmalogical Basis of Therapeutics, The Macmillan Co., New York, 1941.  50  Gorriti, R., Medina, A., cited Kornblueh, I.H., Griffin, J.E., Amer. Jour. Physic. Med., 34:618, 1955.  51  Green, D.M.,  52  Grollman, A., Amer. J. Physiol., 147:647, 1946.  53  Grollman, A., J. Pharmacol, and Exper. Therap., 39:313, 1930.  54  Grollman, A., et a l , Amer. J. Physiol., 157:21, 1949.  55  Grollman, A., Perspectives of B i o l . & Med., Winter, 1959.  J.A.M.A., 131:1260, 1946.  vol. II (2):208. 56  Gross, F., Klin. Wehnschr., 36:693, 1958.  57  Hallander, W., Wilkins, R.W.,  58  Haddy et a l , Cir. Res., 7:123, 195*9.  59  Hamilton, J.W.,  60  Haus, W.H.,  Boston, Med. Quart., 8:69, 1957.  Grollman, A., J. Biol. Chem., 233:528, 1958.  et a l cited Smirk, High Arterial-blood Pressure,  Blackwell, Oxford, 1957. 61  Hawthorne, E.W.,  et a l , Am. J. Physiol., 174:393, 1953.  62  Hawthorne, E.W.,  Green, C.S., Fed. P r o c , 15:89, 1956.  63  Helmer, O.M.,  G r i f f i t h , R.S., Fed. P r o c , 10:196, 1951.  64  Helmer, O.M.,  Fed. P r o c , 14:728, 195.5.  65  Hering, H.E., Dresden: Steinkopff cited Pickering, G.W., High Blood Pressure, Grune and Stratton, New York, 1955, p.117. Hering, H.E. Munch. Med. Wschr., 77=7, 1930 cited Smirk,  66  High Arterial Pressure, Blackwell, Oxford, 1957. 67  Heymans, G., New Eng. J. Med., 219:154, 1938.  68  Holton, P., Jour. Physiol., 108:525, 1949.  69  Hoobler, S.W.,  70 71 72  Horst, K., et a l , Jour, of Pharm. and Exper. Therap., 52:307, 1934. Johnson, T.B., Tewkesbury, L.B., Proc. Nat. Acad. Sci., 28:73, 1942. Kezdi, P., Wennemark, J.R., C i r c , 17:785, 1958.  C i r c , 17:525, 1958.  58 73  Knowlton, A.I., et a l , J . Exper. Med., 96:187, 1952.  74  Koch, E., Mies, H. Krankheitsforschung, 7*241, 1929 cited Corcoran, A.C., C.M.A.J., 81, 145, 1959.  75  Kohlstaedt, K.G., et a l , Proc. Soc. Exp. Biol. & Med., 39:214, 1938.  76 77  Kohlstaedt, K.G., Page, I.H., Jour. Exper. Med., 72:201, 1940. Kolf, W.J., et a l , Am. J . Physiol., 178:237, 1954.  78  Kornblueh, I.H. G r i f f i n , J.E., Amer. Jour. Physic. Med., 34:618, 1955.  79  Kornblueh, I.H., et a l , Amer. Jour. Physic. Med., 37:18, 1958.  80  Krueger, A.P., et a l , Jour. Gen. Physiol., 41:359, 1957.  81  Kuntzman, R., et a l , Fed. P r o c , 15:450, 1956.  82  Labbe, M., et a l , Bull. S o c Med. Hop., Paris, 46:982, 1922, cited Smirk, High Arterial Blood Pressure, Blackwell, Oxford.  83  Lang, G.F., Hypertensive disease, Moscow, 1950 cited Simonson, E., Brozek, J., Annals, of Int. Med., 50:129, 1959.  84  Lee, R.E., Schneider, R.F., J.A.M.A., 167:1447, 1958.  85  Lewis, H.A., Goldblatt, H., Bull. N.Y. Acad. Med., 18:459, 1942.  86  Luetscher, J.A., Johnson, B.B., J . Clin. Invest., 32:585, 1953.  87  McCubbin, J.W., et a l , C i r c Res., 4:205, 1956.  88  Martin, T.L-., Else. Eng., 7-3*28, 1954.  89  Mason, G., et a l , Endocrin, 62:229, 1958.  90  , Megbow, R.S., Jour. Mt. Sinai Hosp., 15:233, 1948.  91  Meneely, G.R., et a l , Ann. Inter. Med., 47:263, 1957.  92  Merrill, J.P., et a l , J.A.M.A., 160:279, 1956.  93  Moses, L., et a l , Psychosom. Med., 18:471, 1956.  94  Neff, A.W., Correll, J.T., Proc. Soc. Exper. Biol, and Med., 95:227, 1957.  95  Ogden, E., Bull. N.Y. Acad. Med., 23:643, 1947.  96  Olsen, N.S., Amer. J . Physiol., 161:448, 1950.  97  Oppenheimer, B.S., Fishberg, A.M., Arch. Inter. Med., 34:631, 1924.  59 98  Page, I.H., Amer. J . Physiol., 122:352, 1938.  99  Page, I.H., et a l , Perspectives i n Biology & Med. vol. 1, Spring, 1958.  100  Page, I.H., Physiol. Rev., 34:563, 1954.  101  Page, I.H., McCubbin, J.W., C i r c , 1:354, 1953.  102  Page, I.H., McCubbin, J.W., C i r c , 4:70, 1951.  103  Page, I.H., HeLmer, O.J., Jour. Exper. Med., 71:29, 1940.  104  Page, I.H., et a l , Jour, of Biol. Chem., 147:143, 1943.  105  Page, I.H., et a l , C i r c , 17:664, 1958.  106  Pitt-Rivers, R., Biochem. Jour., 43:223, 1948.  107  Pickering, G.W.,  108  Raab, W., Neurogenic and Hormonal Cardiovascular Disorders,  Prinzmetal, M., Clin. Sci., 3-357, 1938.  Baltimore, Williams & Wilkins, 1953. 109  Redleaf, P.D., Tabian, L., Circ. Res., 6:185, 1958..  110  Redish, W., et a l , C i r c , 17:208, 1958.  111  R i t t e l , W., et a l , Helvet. Chem. Acta., 40:614, 1957.  112  Rixon, R.H., M.A. Thesis. University of British Columbia, 1950.  113  Rondel, P.A., et a l , C i r c , 17:708, 1958.  114 115  Rosenfeld, S.., Amer. J . Physiol., 169:733* 1952. Rothlin, E., et a l , Acta. Med. Scand., Supp. (312), 154:27, 1956.  116  Russi, S., et a l , Arch. Inter. Med., 76:284, 1945.  .117  Salter, W.T., Textbook of Pharmacology, W.B. Saunders Co., London & Philadelphia, 1953.  118  Sapirstein, L.A., et a l , Proc. Soc. Exper. Biol, and Med., 73:82, 1950.  119  Schrodir, H.A., Mechanisms of Hypertension, C.C. Thomas, I l l i n o i s , 1957. p . 3 l .  120  Selye, H., Hypertension, a Symposium, Bell, E.T. Minneapolis. Univ. Minnesota Press, 1951, pp. 119-132.  121  Selye, H., Hypertension, a Symposium, Brit. M.J., 1:203, 1950.  122  Shore, P.A., Ann. N.Y. Acad. Sci., 66 Ant. 3 , 1956.  60 123  Simonson, E., Brozek, J., Annals, of Int. Med., 50:129, 1959.  124  Sjostrom, E., Nykanen, L., Jour, of Amer. Pharmaceutical Assoc., Scientific ed., 47-*248, 195®.  125  Skegg, L.T., Kahn, J.R., J . Exper. Med., 95:523, 1952.  126  Skegg, L.T., Kahn, J.R., C i r c , 17:658, 1958.  127  Skegg, L.T., et a l , Jour, of Exper. Med., 103:295, 1956.  .128  Skegg, L.T., et a l , Jour, of Exper. Med., 106:439, 1957.  129  ' Skelton, F.R., Circ. Res., 7:107, 1959.  130  Skelton, F.R., Endocrin, 62:365, 1958.  131  Skelton, F.R., A.M.A. Arch. Int. Med., 98:449, 1956.  132  Skelton, F.R., Physiol. Rev., 39:162, 1959.  133 134  Stamler, J., Katz, L.N., C i r c , 3:859, 1956. Taquini, A.C, Fasciolo, J.C., Rev. Argent de Cardio, cited Tarquini et a l , C i r c , 17:672, 1958.  135  Tehijevsky, A.L., Acta. Med. Scand., 99-117-139, 1939.  136  Tigerstedt, R., Bergman, P.C, Skand. Arch. Physiol., 8:223, 1898. cited Turner, C.D., General Endocrinology, Saunders, W.B., Co., Philadelphia & London, 1959.  137  Tobian, L., Binion, J.T., J . Clin. Invest., 33:1407, 1954.  138  Wakerlin, G.E., Physiol. Rev., 34:555, 1955.  139  Wakerlin, G.E., Proc Soc. Exper. Biol. Med., 90:99, 1955.  140  Wakerlin, G.E., C i r c , 17:653, 1958.  141  Wakerlin, G.E., et a l , Circ. Res., 2:416, 1954.  142  Walter, C.W.,  143  Weller, J.M., Hoobler, S.W.,  144  Weller, J.M., et, a l , U iv. Michigan, M d. Bull., 24:44, 1958.  145  Wilson, C , Lancet, i i : 5 7 9 , 1953*  146  Wilson, A., Schild, H.O., Applied Pharmacology, J . & A. Churchill Ltd., London, 1959, 9th Ed.  Pijoan, M.J., Surgery, 1:282, 1937. Ann. of Inter. Med.,  n  50:106, 1959.  e  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0106103/manifest

Comment

Related Items