토끼에 있어 혈압변동에 따른 레닌-안지오텐신 활성도의 변화

Abstract

Renal perfusion experiments were performed in the isolated rabbit kidneys. in order to investigate the mechanism of renal autoregulation and determine the intrarenal existence of converting enzyme. In a series of experiments. perfusion pressure was lowered to 100 mm Hg from the control level of 150 mm Hg and maintained for 12 minutes and again returned to the control level of 150 mm Hg• In another series of experiments. perfusion pressure was kept at 70 mm Hg for 12 minutes. During each period, renal arterial and venous blood were collected simultaneously at the last 2 minutes. Measurement of RBF was done directly by means of a flowmeter. Immediately after the experiment'. kidney was weighed. and cortex and medul1a were separated to measure the renin activities. Renin activities were measured by the technique of radioimmunoassay. The secretion rate of renin was calculated from RBF and arteriovenous difference of renin activities. In the experiments which perfusion pressure was maintained at 100 mm Hg, the secretion rate of renin showed no significant changes (from 17.8 to 24.5 rig/min). This data indicates that the changes in perfusion pressure within the range of autoregulation responded no significant alterations of renin secretion. In the experiments kept at 70 mm Hg, however, the secretion rate of renin was increased over five times (from 17.6 to 112.5 ng/min). This result demonstrated that the changes in perfusion pressure out of range of renal autoregulation resulted in the severe renin secretion. Angiotensin I activities in the cortex and meduIla were 1.63 and 4.03 ng/ml·hr·gm wet tissue. rea-' pectively. But angiotensin II activities were measured only in the cortex (29.55 ng/l00mI'gm wet tissue). not detected at all in the meduIla. The findings of this study suggest that renin may playa physiologically important role in restoring the blood pressure to the pressure within the range of renal autoregulation. The fact that angiotensin II was measurable only in the cortex. may reveal that the converting enzyme is present in the renal cortex.