RELATION OF ARTERIAL-PRESSURE AND PLASMA ANGIOTENSIN-II CONCENTRATION - CHANGE PRODUCED BY PROLONGED INFUSION OF ANGIOTENSIN-II IN THE CONSCIOUS DOG

Five unrestrained male beagle dogs were given a continuous intravenous infusion for 28 days. First, 0.9% NaCl solution was infused for 7 days, then angiotensin II at 3 ng/kg per min for 14 days, and finally 0.9% NaCl for 7 days. The authors found that the blood pressure rose gradually in each dog, reaching a peak toward the end of the 14-day infusion of angiotensin II. When angiotensin infusion was stopped, blood pressure fell gradually during 24 hours; the lowest pressure was not reached until 5 days later. To assess the relation between plasma angiotensin II concentration and arterial pressure, dose-response studies were done during the first saline infusion, after 7 and 14 days of angiotensin II infusion, and at the end of the second saline infusion. In these experiments, additional angiotensin II was infused intravenously at 3, 6, and 12 ng/kg per min, each rate for 1 hour. The increase of arterial pressure was then related to concurrent plasma angiotensin II concentration. In all dogs, prolonged infusion of angiotensin shifted the position of this curve upward. Thus, prolonged infusion of angiotensin raised the level of pressure maintained by a given plasma concentration of angiotensin II. Seven days after the angiotensin infusion, the curve had returned to the original position. Plasma aldosterone concentration also increased during all dose-response studies. The slope of the regression curve relating plasma concentrations of angiotensin II and aldosterone was steeper after, but not during, prolonged infusion of angiotensin II. Plasma potassium concentration did not change at any stage.