Effect of selective angiotensin antagonists on the antidiuresis produced by angiotensin-(1-7) in water-loaded rats.
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 (CCr: 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 CCr 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 CCr 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.
Baracho
N C
NC
Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais, Belo Horizonte, Brasil.
Simões-e-Silva
A C
AC
Khosla
M C
MC
Santos
R A
RA
D000704:Analysis of Variance; D000803:Angiotensin I; D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000494:pharmacology / Q000502:physiology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D004231:Diuresis / Q000187:drug effects*; D004326:Drinking; D007668:Kidney / Q000187:drug effects; D019808:Losartan / Q000494:pharmacology*; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011945:Receptors, Angiotensin / Q000502:physiology*; D012076:Renal Agents / Q000037:antagonists & inhibitors* / Q000494:pharmacology
C092006:7-Ala-angiotensin (1-7); D057911:Angiotensin Receptor Antagonists; D010446:Peptide Fragments; D011945:Receptors, Angiotensin; D012076:Renal Agents; D000804:Angiotensin II; D000803:Angiotensin I; C118790:angiotensin I (1-7); D019808:Losartan