Evidence that the effects of isoproterenol on water intake and vasopressin secretion are mediated by angiotensin.

The effect of isoproterenol (6 microgram/kg sc) on drinking, urine flow, and vasopressin secretion was examined in a group of trained dogs with chronically implanted third ventricular cannulae. Isoproterenol stimulated drinking in association with a reduction in urine flow and an increase in urine to plasma osmolality ratio. Plasma renin activity increased from 3.1 +/- 0.8 to 13.0 +/- 2.7 ng/ml/3 h and plasma vasopressin concentration increased from 11.3 +/- 1.3 to 40.3 +/- 12.5 pg/ml. The effect of isoproterenol was reexamined during an intracerebroventricular infusion of the angiotensin II antagonist, saralasin (0.02 microgram/kg/min). This treatment did not affect the isoproterenol-induced increase in plasma renin activity, but inhibited the drinking, antidiuresis, and increase in plasma vasopressin concentration. These data indicate that the effects of isoproterenol on drinking, urine flow, and vasopressin secretion are mediated via the renin-angiotensin system.