Effect of prolonged angiotensin II infusion on thirst

To determine the effect of prolonged angiotensin II (A-II) infusion on thirst, daily water intake by drinking was measured in dogs during a 4-day control period, a 4-day period of vehicle infusion without A-II, a 10-day period of A-II infusion, and a 4-day recovery period of vehicle infusion without A-II. During the control period and the periods of vehicle infusion in the absence of A-II, daily water intake by drinking in four dogs averaged 118 +/- 20 ml/day (mean +/- SE). During the 10-day period of A-II infusion at the rate of 13.0 ng/kg per min drinking increased to 269 +/- 49 ml/day (paired t; P less than 0.05). Angiotensin II infusion at the rate of 26.0 ng/kg per min produced a sustained increase in water intake in two dogs during an 8-day period of infusion. These results demonstrate that in dogs, prolonged infusion of angiotensin II stimulates the thirst mechanism and that the effect lasts for more than a few days.