Renin, Aldosterone, Body Fluid Volumes, and the Baroreceptor Reflex in the Development and Reversal of Goldblatt Hypertension in Conscious Dogs

Abstract

The renal artery to a sole remaining kidney was constricted in unanesthetized dogs while renal arterial pressure was recorded distal to the occluder. Following the constriction, mean arterial blood pressure, which was continuously monitored 24 hours a day for 1 week, exhibited a biphasic increase. The first peak in pressure correlated with a large increase in plasma renin activity; the second peak correlated with an increase in plasma volume brought about by positive sodium and water balances. Renin activity was returning to normal when the second peak occurred. Increased drinking played a major role in the positive water balance. Plasma aldosterone concentration was moderately and transiently increased for only a few hours following the constriction. The experiment was repeated in sinoaortic baroreceptor-denervated dogs; apparently, the baroreceptor reflex significantly slows the time course of the arterial blood pressure increase during the first few days of constriction but does not alter the magnitude of the pressure increase after 1 week. After release of renal artery constriction, mean arterial blood pressure decreased progressively over a 3-day period, during which time significant negative sodium and fluid balance occurred. The slow return of the pressure back to normal correlated highly with a decrease in plasma volume. In the baroreceptor-denervated dogs, the initial fall in arterial blood pressure apparently also resulted at least partly from a decrease in plasma renin activity, but this effect was not observed in the intact dogs because the renin activities in these dogs had already decreased to normal prior to constrictor release. The effects of the baroreceptor reflex on the time course of the pressure decrease did not seem to be as significant as those on the time course of the pressure increase.