Effects of inhibitors of the renin-angiotensin system on water intake after insulin administration.

Male wistar rats drank in a dose-related manner, in response to 1 to 40 U/kg of i.p. insulin. Maximum intakes took place during the first 30 min after i.p. insulin administration, coinciding with the period of maximal drop of blood glucose. Plasma renin activity (PRA) in rats treated with i.p. insulin was higher than in basal conditions or after saline injection. Nephrectomy and adrenalectomy did not abolish insulin-induced drinking. A low dose of captopril (0.1 mg/kg s.c.) did not modify insulin-induced drinking, but a higher dose (10 mg/kg s.c.), or enalapril (0.5 mg/microgram s.c.), significantly increased insulin-induced drinking. Enhancement of insulin-induced drinking by s.c. captopril was not secondary to an increased diuresis. Captopril (50 micrograms i.c.v.) significantly reduced the cumulative water intake after i.p. insulin (20 U/kg i.p.) plus s.c. captopril (10 mg/kg). The blockade of central receptors for angiotensin II with sarile-AII (5 micrograms) significantly diminished insulin-induced drinking. It appears that the peripheral renin angiotensin system is not necessary for insulin-induced drinking but central angiotensin II plays an important role.