The relation of arterial pressure and plasma angiotensin II concentration. A change produced by prolonged infusion of angiotensin II in the conscious dog.

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Abstract
Unrestrained male beagle dogs (5) were given a continuous i.v. 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 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 h; the lowest pressure was reached 5 days later. To assess the relation between plasma angiotensin II concentration and arterial pressure, dose-response studies were done during the 1st saline infusion, after 7 and 14 days of angiotensin II infusion, and at the end of the 2nd saline infusion. Additional angiotensin II was infused i.v. at 3, 6 and 12 n/kg per min, each rate for 1 h. The increase of arterial pressure was then related to concorrent plasma angiotensin II concentration. In all dogs, prolonged infusion of angiotensin shifted the position of the curve upward. Prolonged infusion of angiotensin raised the level of pressure maintained by a given plasma concentration of angiogensin II. The curve returned to the original position 7 days after the angiotensin infusion. 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 prolonged infusion of angiotensin II. Plasma K concentration did not change at any stage.