AJP - Renal Physiology, Vol 245, Issue 6 784-F791, Copyright © 1983 by American Physiological Society
Effects of variations in renal hemodynamics on the time course of renin secretion rate
S. Simchon and S. Chien
The effects of variations in renal hemodynamics on the time course of renin
secretion were studied in dogs anesthetized with pentobarbital-chloralose.
Hemodynamic changes were induced either locally in kidneys perfused in situ
via an extracorporeal circuit (with or without a pump system) or
systemically by hemorrhage or nitroprusside infusion. In the autoperfused
kidney the reduction of renal perfusion pressure to approximately one-half
of the arterial pressure by inflow occlusion caused an increase in renal
conductance (renal vasodilation) and an increase in renin secretion rate
(RSR). In the pump-perfused kidney, a step increase in renal blood flow
(RBF) caused renal vasoconstriction and a decrease in RSR; a step decrease
in RBF caused renal vasodilation and an increase in RSR. Following step
changes in RBF, the time constant of the alterations of renal conductance
was 56.5 s, and the time constant of the RSR responses was 80.1 s. The
total time required to reach a steady state for RSR lagged behind that for
renal conductance by approximately 5 min. These differences reflect the
time needed for the kidney to release renin in response to changes in renal
vascular caliber. The results suggest that renin release occurs in response
to the autoregulatory dilation of the renal arterioles. When systemic
hypotension was induced by nitroprusside infusion, RSR also increased
together with the renal conductance. Following hemorrhage, however, RSR
increased despite a decrease in renal conductance, reflecting the role of
neurohumoral factors in causing renin release in this case. The comparison
of renin secretion following different types of hemodynamic alterations
serves to elucidate the mechanisms of renin secretion.
