Effect of selective angiotensin antagonists on the antidiuresis produced by angiotensin-(1-7) in water-loaded rats

Braz J Med Biol Res, September 1998, Volume 31(9) 1221-1227

Effect of selective angiotensin antagonists on the antidiuresis produced by angiotensin-(1-7) in water-loaded rats

N.C.V. Baracho¹, A.C. Simões-e-Silva¹, M.C. Khosla² and R.A.S. Santos¹

¹Laboratório de Hipertensão, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil

²Department of Neuroscience, Cleveland Clinic Foundation, Cleveland, OH, USA

References

Abstract

Introduction

Material and Methods

Results

Discussion

Acknowledgments

^{Correspondence and Footnotes}

In the present study we evaluated the nature of angiotensin receptors involved in the antidiuretic effect of angiotensin-(1-7) (Ang-(1-7)) in water-loaded rats. Water diuresis was induced in male Wistar rats weighing 280 to 320 g by water load (5 ml/100 g body weight by gavage). Immediately after water load the rats were treated subcutaneously with (doses are per 100 g body weight): 1) vehicle (0.05 ml 0.9% NaCl); 2) graded doses of 20, 40 or 80 pmol Ang-(1-7); 3) 200 nmol Losartan; 4) 200 nmol Losartan combined with 40 pmol Ang-(1-7); 5) 1.1 or 4.4 nmol A-779; 6) 1.1 nmol A-779 combined with graded doses of 20, 40 or 80 pmol Ang-(1-7); 7) 4.4 nmol A-779 combined with graded doses of 20, 40 or 80 pmol Ang-(1-7); 8) 95 nmol CGP 42112A, or 9) 95 nmol CGP 42112A combined with 40 pmol Ang-(1-7). The antidiuretic effect of Ang-(1-7) was associated with an increase in urinary Na⁺ concentration, an increase in urinary osmolality and a reduction in creatinine clearance (C_Cr: 0.65 ± 0.04 ml/min vs 1.45 ± 0.18 ml/min in vehicle-treated rats, P<0.05). A-779 and Losartan completely blocked the effect of Ang-(1-7) on water diuresis (2.93 ± 0.34 ml/60 min and 3.39 ± 0.58 ml/60 min, respectively). CGP 42112A, at the dose used, did not modify the antidiuretic effect of Ang-(1-7). The blockade produced by Losartan was associated with an increase in C_Cr and with an increase in sodium and water excretion as compared with Ang-(1-7)-treated rats. When Ang-(1-7) was combined with A-779 there was an increase in C_Cr and natriuresis and a reduction in urine osmolality compared with rats treated with Ang-(1-7) alone. The observation that both A-779, which does not bind to AT₁ receptors, and Losartan blocked the effect of Ang-(1-7) suggests that the kidney effects of Ang-(1-7) are mediated by a non-AT₁ angiotensin receptor that is recognized by Losartan.

Key words: renin-angiotensin system, angiotensin receptors, antidiuresis, losartan, A-779, Ang-(1-7)

The heptapeptide angiotensin-(1-7) (Ang-(1-7)) is a recently identified active component of the renin-angiotensin system that can be formed by a route independent of angiotensin converting enzyme (1-3). Ang-(1-7) has been demonstrated in plasma and tissues of a variety of species, including man, dogs, sheep and rats (3-5).

In addition to the different enzymatic route for its generation, Ang-(1-7) differs importantly from Ang II by its selectivity. Although both peptides elicit some similar actions in the brain, such as changes in blood pressure (6-8) and an increase in neuronal activity (9), Ang-(1-7) is devoid of significant dipsogenic, vasoconstrictor or aldosterone secretagogue actions (see Ref. 2 for review). Ang-(1-7) can even present effects opposite to those of Ang II, such as those on the baroreceptor reflex sensitivity which is attenuated by Ang II and increased by Ang-(1-7) (10).

A growing body of evidence suggests that one of the major physiological actions of Ang-(1-7) is related to the control of hydroelectrolyte balance. Dense immunostaining for Ang-(1-7) immunoreactivity has been demonstrated in the supraoptic and paraventricular nuclei of the hypothalamus and neurohypophysical (11), and Ang-(1-7) is as potent as Ang II in releasing AVP from hypothalamus-neurohypophysial explants (12). In addition, we have shown that Ang-(1-7) possesses a potent peripheral antidiuretic activity in water-loaded rats that is not influenced by blockade of vasopressin V₂ receptors (13,14). In vitro, Ang-(1-7) has been reported to increase four-fold the hydraulic conductivity in intramedullary collecting ducts at a concentration of 10^-9 mol/l (14). In the proximal straight tubule Ang-(1-7) increases fluid and bicarbonate reabsorption at physiological concentrations (10^-12 mol/l) (15).

In addition to water excretion, Ang-(1-7) appears to influence sodium handling by the kidneys. A natriuretic effect of supra-physiological doses of Ang-(1-7) has been reported in denervated kidneys (16) in vivo and in in situ perfused rat kidneys (17). The natriuretic effect of Ang-(1-7) in these preparations is in accordance with the observation that 10^-9 mol/l Ang-(1-7) inhibits (20%) Na⁺ flux in cultured renal tubular epithelial cells (18). A physiological role for Ang-(1-7) in the control of hydromineral balance is also suggested by the selective increase in its circulating levels in chronically salt-loaded rats (5). Moreover, the enzymes necessary to generate Ang-(1-7) from its precursors (Ang I or Ang II) are abundant in the kidney (19).

We have recently shown that the antidiuretic effect of Ang-(1-7) in water-loaded rats is completely blocked by the selective Ang-(1-7) antagonist A-779 (14,20). However, the effect of other selective angiotensin antagonists on the antidiuretic activity of this heptapeptide is not known. In this study we evaluated the nature of angiotensin receptors involved in the antidiuretic effect of Ang-(1-7) in water-loaded rats.

Animals

Male Wistar rats weighing 280 to 320 g were used. The rats were housed in plastic cages with free access to ordinary chow and water, on a 14/10 h light/dark cycle.

Effect of angiotensin antagonists on antidiuretic action of Ang-(1-7) in water-loaded rats

Protocol 1: Effect of Losartan on the antidiuretic action of Ang-(1-7). Water diuresis was induced by water load (5 ml/100 g body weight by gavage). Immediately after the water load, the animals were treated subcutaneously with vehicle (0.05 ml 0.9% NaCl/100 g body weight, N = 27), 200 nmol Losartan/100 g body weight (N = 15), 40 pmol Ang-(1-7)/100 g body weight (N = 32) or 200 nmol Losartan/100 g body weight associated with 40 pmol Ang-(1-7)/100 g body weight (N = 24). Urine volume was collected for 60 min after water loading.

Protocol 2: Effect of A-779 on the antidiuretic action of Ang-(1-7). Immediately after the water load rats were treated subcutaneously with 1) Ang-(1-7) alone, 20 (N = 6), 40 (N = 27) or 80 pmol/100 g body weight (N = 6); 2) A-779 alone, 1.1 (N = 18) or 4.4 nmol/100 g body weight (N = 14); 3) 1.1 nmol A-779/100 g body weight combined with different doses of Ang-(1-7) (20 (N = 6), 40 (N = 10) and 80 pmol/100 g body weight (N = 6)), or 4) 4.4 nmol A-779/100 g body weight combined with graded doses of Ang-(1-7) (20 (N = 6), 40 (N = 9) and 80 pmol/100 g body weight (N = 6)). Urine volume was collected and measured 60 min after water loading.

Protocol 3: Effect of CGP 42112A on the antidiuretic action of Ang-(1-7). Immediately after the water load rats were treated subcutaneously with 95 nmol CGP 42112A/100 g body weight (N = 8) or 95 nmol CGP 42112A/100 g body weight combined with 40 pmol Ang-(1-7)/100 g body weight (N = 24). Urine volume was collected and measured 60 min after water loading.

Mechanism involved in the blockade of the antidiuretic action of Ang-(1-7) in water-loaded rats

Protocol 1: Effect of Losartan on renal function parameters. Immediately after water loading, other groups of animals were treated subcutaneously with vehicle (0.05 ml 0.9% NaCl/100 g body weight, N = 17), 40 pmol Ang-(1-7)/100 g body weight (N = 16), 200 nmol Losartan/100 g body weight (N = 9) or 200 nmol Losartan/100 g body weight associated with 40 pmol Ang-(1-7)/100 g body weight (N = 10) and transferred to metabolic cages. Blood and urine samples for the measurement of creatinine clearance (C_Cr), osmolality, and sodium concentration were collected 60 min after water loading.

Protocol 2: Effect of A-779 on renal function parameters. Immediately after water loading, additional groups of rats were treated subcutaneously with 4.4 nmol A-779/100 g body weight (N = 9) or 4.4 nmol A-779/100 g body weight combined with 40 pmol Ang-(1-7)/100 g body weight (N = 10) and transferred to metabolic cages. Blood and urine samples for measurement of C_Cr, osmolality, and sodium concentration were collected 60 min after water loading.

General procedures

Blood sampling. Immediately after urine collection, the rats were anesthetized with ether and blood samples were withdrawn by heart puncture. Blood samples were kept for 30 min at room temperature and then centrifuged at 2000 rpm for 10 min. Serum was used for measurement of serum osmolality, Na⁺ and creatinine concentration.

Urine samples. After collection, the urine samples were centrifuged at 3000 rpm for 5 min (room temperature) for measurement of urine osmolality, Na⁺ and creatinine concentration.

Analytical procedures

Sodium was measured by flame photometry (Corning 400, Corning Inc., New York, NY). Serum and urine osmolality were measured using a freezing-point Osmometer (Fiske Associates, Norwood, MA). Creatinine clearance measurements were performed using a kit which minimizes the interference of endogenous chromogens (cat. 35E, Labtest, Belo Horizonte, MG).

Chemicals

The nonpeptide AT₁ receptor antagonist, Losartan (molecular mass = 461), was a gift from Du Pont de Nemours & Company (Wilmington, DE) and the AT₂ receptor antagonist, CGP 42112A (molecular mass = 1053), was provided by Ciba-Geigy Limited (Basel, Switzerland). The Ang-(1-7) analogue, A-779 (molecular mass = 873.1), was synthesized by Dr. M.C. Khosla (Cleveland Clinic Foundation). Ang-(1-7) (molecular mass = 890) was synthesized by Dr. M.C. Khosla or obtained from Bachem (Batch # 25691; Torrance, CA). All other chemicals used were of the highest purity available.

Statistical analysis

All results are reported as means ± SEM. Data were analyzed using one-way analysis of variance (ANOVA) followed by the Newman-Keuls test. The level of significance was set at P<0.05.

Effect of angiotensin antagonists on the antidiuretic action of Ang-(1-7) in water-loaded rats

Blockade of the antidiuretic effect of Ang-(1-7). As shown in Figure 1, Losartan completely blocked the antidiuretic effect of Ang-(1-7) in water-loaded rats. Losartan alone, at the dose used, did not change water diuresis compared to vehicle-treated rats.

The effect of the two doses of A-779 (1.1 and 4.4 nmol/100 g body weight) on the antidiuretic action of graded doses of Ang-(1-7) (20 to 80 pmol/100 g body weight) is shown in Figure 2. A-779 completely blocked the antidiuretic effect of Ang-(1-7) in water-loaded rats at both doses used. A-779 given alone produced an increase in water diuresis compared with vehicle-treated rats at the highest dose (4.4 nmol/100 g body weight).

As shown in Figure 3, the AT₂ ligand, CGP 42112A, did not change water diuresis or the antidiuretic effect of Ang-(1-7) in water-loaded rats.

Figure 1
- Effect of Losartan on the antidiuretic action of Ang-(1-7). Immediately after water load, rats were treated subcutaneously with vehicle (saline, N = 27), 200 nmol Losartan/100 g body weight (N = 15), 40 pmol Ang-(1-7)/100 g body weight (N = 32) or 200 nmol Losartan/100 g body weight combined with 40 pmol Ang-(1-7)/100 g body weight (N = 24). Urine was collected 60 min after water loading. Data are reported as means ± SEM. *P<0.05 compared with saline-treated group (ANOVA followed by the Newman-Keuls test).

Figure 2
- Effect of A-779 on the antidiuretic action of Ang-(1-7). Immediately after water load, rats were treated subcutaneously with vehicle (saline, N = 27); graded doses of Ang-(1-7) alone, 20 (N = 6), 40 (N = 27) and 80 pmol/100 g body weight (N = 6); 1.1 nmol A-779/100 g body weight (N = 18); 4.4 nmol A-779/100 g body weight (N = 14); 1.1 nmol A-779/100 g body weight combined with graded doses of Ang-(1-7) (20 (N = 6), 40 (N = 10) and 80 pmol/100 g body weight (N = 6)); or 4.4 nmol A-779/100 g body weight combined with graded doses of Ang-(1-7) (20 (N = 6), 40 (N = 9) and 80 pmol/100 g body weight (N = 6)). Urine was collected 60 min after water loading. Data are reported as means ± SEM. *P<0.05 compared with saline-treated group (ANOVA followed by the Newman-Keuls test).

Figure 3
- Effect of CGP 42112A on the antidiuretic action of Ang-(1-7). Immediately after water load, rats were treated subcutaneously with vehicle (saline, N = 27), 40 pmol Ang-(1-7)/100 g body weight (N = 32), 95 nmol CGP 42112A/100 g body weight (N = 8) or 95 nmol CGP 42112A/100 g body weight combined with 40 pmol Ang-(1-7)/100 g body weight (N = 24). Urine was collected 60 min after water loading. Data are reported as means ± SEM. *P<0.05 compared with saline-treated group (ANOVA followed by the Newman-Keuls test).

Mechanisms involved in the blockade of the antidiuretic action of Ang-(1-7) in water-loaded rats

Effect of Losartan on renal function parameters. The effect of Losartan on renal function parameters in water-loaded rats is shown in Table 1. Losartan blockade of the antidiuretic effect of Ang-(1-7) was associated with a significant increase in creatinine clearance and in sodium and water excretion compared with Ang-(1-7)-treated rats (P<0.05).

Effect of A-779 on renal function parameters. The effect of A-779 on renal function parameters in water-loaded rats is shown in Table 1. The increase in water diuresis produced by A-779 given alone was associated with a decrease in urine osmolality and natriuresis and an increase in creatinine clearance compared with vehicle-treated rats. The results obtained with the combination of A-779 and Ang-(1-7) did not differ from those obtained with A-779 alone.

We have previously shown that the antidiuretic effect of Ang-(1-7) in water-loaded rats was completely blocked by the Ang-(1-7) selective antagonist, A-779 (14,20). In the present study we extended this observation by showing that Losartan, an AT₁ receptor antagonist, also blocked the antidiuretic effect of Ang-(1-7) in water-loaded rats.

The antidiuretic effect of Ang-(1-7) in water-loaded rats was associated with a decrease in creatinine clearance and an increase in water reabsorption. Both A-779 and Losartan blocked the antidiuretic effect by preventing the changes in creatinine clearance and in sodium and water excretion produced by Ang-(1-7).

Our observation that Losartan blocked the antidiuretic effect of Ang-(1-7) is consistent with other studies. Garcia and Garvin (15) found that the effects of Ang-(1-7) on fluid and bicarbonate absorption in isolated proximal straight tubules were blocked by Losartan. A partial blockade of the effect of Ang-(1-7) on O₂ consumption in rat proximal tubules was also observed by Handa et al. (16). Similar findings were obtained in the heart by Gironacci et al. (21). These data raised two possible explanations: 1) Ang-(1-7) may act through AT₁ receptors or 2) Losartan can block a subtype of Ang-(1-7) receptor. The first explanation is unlikely since Ang-(1-7) does not exert most of the Ang II actions that are mediated through AT₁ receptors, i.e., vasoconstriction and induction of drinking (4) and Ang-(1-7) binds poorly to AT₁ receptors (3,20). The second possibility is more likely because it is reasonable to conceive that the still unidentified renal Ang-(1-7) receptor(s) can resemble AT₁ receptors and that Losartan can bind to it (them). This second possibility was also substantiated by recent observations that have raised concerns about the specificity of Losartan (22-24). It was shown that this compound can bind to non-angiotensin II binding sites (22) or interfere with non-angiotensin-mediated responses (23). In addition, differential regulation of Ang II and Losartan binding sites was observed in rat glomeruli and human mesangial cells (24). The recent observation that Losartan can block thromboxane A₂ receptors further indicates a lack of specificity of this angiotensin AT₁ receptor ligand (25).

The finding that both Losartan and A-779 can block the antidiuretic effect of Ang-(1-7) suggests the existence of at least two subtypes of Ang-(1-7) receptors: one which is expressed, for example, in blood vessels (26) and the brain (rostral ventrolateral medulla and caudal pressor area) (10,20) and is not blocked by AT₁ or AT₂ antagonists (10,20), and the other expressed at sites such as the hypothalamus (27), heart (21) and the kidney (15) which can be blocked by Losartan and to a variable extent by AT₂ ligands. Nevertheless, the observation that Losartan can block at least some of the Ang-(1-7) effects on the kidney raises the intriguing possibility that blockade of endogenous Ang-(1-7) can contribute to its pharmacological effects.

Administration of A-779 alone at a dose of 4.4 nmol/100 g body weight increased water diuresis, suggesting that even in this condition, unlike vasopressin, whose plasma levels are suppressed (28), endogenous Ang-(1-7) can modulate water excretion. However, an agonistic effect of A-779 at this dose or a synergistic effect with other peptides, although unlikely, cannot be ruled out.

We are thankful to José R. Silva and Soraia S. Silva for skillful technical assistance.

Address for correspondence: R.A.S. Santos, Departamento de Fisiologia e Biofísica, ICB, UFMG, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, MG, Brasil. Fax: [phone]. E-mail: [e-mail]

Presented at the II International Symposium on Vasoactive Peptides, Ouro Preto, MG, Brasil, October 6-8, 1997. Research supported by FAPEMIG, PRONEX, CNPq and CAPES. N.C.V. Baracho and A.C. Simões-e-Silva were recipients of CNPq fellowships. Received April 7, 1998. Accepted May 4, 1998.

• 1. Ferrario CM, Barnes KL, Block CH, Brosnihan KB, Diz DI, Khosla MC & Santos RAS (1990). Pathways of angiotensin formation and function in the brain. Hypertension, 15: I-13-I-19.
• 2. Santos RAS & Campagnole-Santos MJ (1994). Central and peripheral actions of angiotensin-(1-7). Brazilian Journal of Medical and Biological Research, 27: 1033-1047.
• 3. Santos RAS, Brosnihan KB, Chappell MC, Pesquero JL, Chernicky CL, Greene LJ & Ferrario CM (1988). Converting enzyme activity and angiotensin metabolism in the dog brainstem. Hypertension, 11: 153-157.
• 4. Santos RAS, Brosnihan KB, Jacobsen DW, DiCorleto PE & Ferrario CM (1992). Production of angiotensin-(1-7) by human vascular endothelium. Hypertension, 19 (Suppl II): II-56-II-61.
• 5. Botelho LM, Block CH, Khosla MC & Santos RAS (1994). Plasma angiotensin-(1-7) level is increased by water deprivation, salt load and hemorrhage. Peptides, 15: 723-729.
• 6. Campagnole-Santos MJ, Diz DI, Santos RAS, Khosla MC, Brosnihan KB & Ferrario CM (1989). Cardiovascular effects of angiotensin (1-7) microinjected into the dorsal medulla of rats. American Journal of Physiology, 257: H324-H329.
• 7. Silva LCS, Fontes MAP, Campagnole-Santos MJ, Khosla MC, Campos Jr RR, Guertzenstein PG & Santos RAS (1993). Cardiovascular effects produced by microinjection of angiotensin-(1-7) on vasopressor and vasodepressor sites of the ventrolateral medulla. Brain Research, 613: 321-325.
• 8. Fontes MAP, Silva LCS, Campagnole-Santos MJ, Khosla MC, Guertzenstein PG & Santos RAS (1994). Evidence that angiotensin-(1-7) plays a role in the central control of blood pressure at the ventro-lateral medulla acting through specific receptor. Brain Research, 665: 175-180.
• 9. Felix D, Khosla MC, Imbodem H, Montani B & Ferrario CM (1991). Neurophysiological responses to angiotensin-(1-7). Hypertension, 17: 1111-1114.
• 10. Campagnole-Santos MJ, Heringer SB, Batista EN, Khosla MC & Santos RAS (1992). Differential baroreceptor reflex modulation by centrally infused angiotensin peptides. American Journal of Physiology, 263: R89-R94.
• 11. Block CH, Santos RAS, Brosnihan KB & Ferrario CM (1988). Immunocytochemical localization of angiotensin (1-7) in the rat forebrain. Peptides, 9: 1395-1401.
• 12. Schiavone MT, Santos RAS, Brosnihan KB, Khosla MC & Ferrario CM (1988). Release of vasopressin from the rat hypothalamo-neurohypophysial system by angiotensin-(1-7) heptapeptide. Proceedings of the National Academy of Sciences, USA, 85: 4095-4098.
• 13. Santos RAS & Baracho NCV (1992). Angiotensin-(1-7) is a potent antidiuretic peptide in rats. Brazilian Journal of Medical and Biological Research, 25: 651-654.
• 14. Santos RAS, Simőes e Silva AC, Magaldi AJ, Cesar KR, Passaglio KT & Baracho NCV (1996). Evidence for a physiological role of angiotensin-(1-7) in the control of hydroelectrolyte balance. Hypertension, 27: 875-884.
• 15. Garcia NH & Garvin JL (1994). Angiotensin-(1-7) has a biphasic effect on fluid absorption in the proximal straight tubule. Journal of the American Society of Nephrology, 5: 1133-1138.
• 16. Handa RK, Ferrario CM & Strandhoy JW (1996). Renal actions of angiotensin-(1-7): in vivo and in vitro studies. American Journal of Physiology, 270 (Renal Fluid and Electrolyte Physiology, 39): F141-F147.
• 17. Dellipizzi A, Hilchley SD, McGiff JC & Bellquilley CP (1994). Natriuretic action of angiotensin-(1-7). British Journal of Pharmacology, 111: 1-4.
• 18. Andreatta-Van Leyen S, Romero MF, Khosla MC & Douglas JG (1993). Modulation of phospholipase A₂ activity and sodium transport by angiotensin-(1-7). Kidney International, 44: 932-936.
• 19. Erdös EG & Skiedgel RA (1990). Renal metabolism of angiotensin I and II. Kidney International, 38: 24-27.
• 20. Santos RAS, Campagnole-Santos MJ, Baracho NCV, Fontes MAP, Silva LCS, Neves LAA, Oliveira DR, Caligiorne SM, Rodrigues ARV, Gropen Jr C, Carvalho WS, Simőes e Silva AC & Khosla MC (1994). Characterization of a new angiotensin antagonist selective for angiotensin-(1-7): Evidence that the actions of angiotensin-(1-7) are mediated by specific angiotensin receptors. Brain Research Bulletin, 35: 293-298.
• 21. Gironacci MM, Adler-Graschinsky E, Peńa C & Enero MA (1994). Effects of angiotensin II and angiotensin-(1-7) on the release of [³H] norepinephrine from rat atria. Hypertension, 24: 457-460.
• 22. Widdowson PS, Renouard A & Vilaine J (1993). Binding of [³H] angiotensin II and [³H] DuP 753 (Losartan) to rat liver homogenates reveals multiple sites. Relationship to AT_1a- and AT_1b-type angiotensin receptors and novel nonangiotensin binding sites. Peptides, 14: 829-837.
• 23. Averill DB, Tsuchihashi T, Khosla MC & Ferrario CM (1994). Losartan, nonpeptide angiotensin II-type 1 (AT₁) receptor antagonist attenuates pressor and sympathoexcitatory responses evoked by angiotensin II and L-glutamate in rostral ventrolateral medulla. Brain Research, 665: 245-252.
• 24. Chansel D, Bizet T, Vandermeersch S, Pham P, Levy B & Ardaillou R (1994). Differential regulation of angiotensin II and losartan binding sites in glomeruli and mesangial cells. American Journal of Physiology, 266: F384-F393.
• 25. Li P, Ferrario CM & Brosnihan KB (1997). Nonpeptide angiotensin II antagonist Losartan inhibits thromboxane A₂-induced contractions in canine coronary arteries. Journal of Pharmacology and Experimental Therapeutics, 281: 1065-1070.
• 26. Pörsti I, Bara AT, Busse R & Hecker M (1994). Release of nitric oxide by angiotensin-(1-7) from porcine coronary endothelium: implications for a novel angiotensin receptor. British Journal of Pharmacology, 111: 652-654.
• 27. Ambühl P, Felix D, Imboden H, Khosla MC & Ferrario CM (1992). Effects of angiotensin analogues and angiotensin receptor antagonists on paraventricular neurones. Regulatory Peptides, 38: 111-120.
• 28. Robertson GL (1985). Osmoregulation of thirst and vasopressin secretion: functional properties and their relationship to water balance. In: Schrier RW (Editor), Vasopressin Raven Press, New York, 203-212.

Correspondence and Footnotes

Publication Dates

• Publication in this collection
  21 Sept 1998
• Date of issue
  Sept 1998

History

• Received
  07 Apr 1998
• Accepted
  04 May 1998