AJP - Endocrinology and Metabolism, Vol 240, Issue 6 682-E688, Copyright © 1981 by American Physiological Society
Inhibition of renin secretion by intrarenal alpha-adrenoceptor blockade
M. L. Blair
This study was designed to determine whether renal alpha-adrenoceptors can
mediate tonic neural stimulation of renin secretion. The effect of
alpha-adrenoceptor blockade by phenoxybenzamine (POB) or prazosin on renin
secretion rate (RSR) was studied in pentobarbital-anesthetized dogs in
which renal perfusion pressure was held constant with an adjustable aortic
clamp. POB alone (100 micrograms.kg-1.min-1 iv) did not change arterial
plasma renin activity (PRA). However, when beta-adrenoceptors were blocked
by intravenous propranolol, intravenous POB infusion (100
micrograms.kg-1.min-1) decreased PRA and RSR to 48 +/- 8 and 21 +/- 9% of
previous levels within 30 min. This effect was abolished by acute bilateral
renal denervation. Direct intrarenal POB infusion (10 or 3.3
micrograms.kg-1.min-1) decreased RSR, whereas intravenous POB (3.3
micrograms.kg-1.min-1) had no effect on either RSR or PRA in
propranolol-pretreated dogs. Prazosin (1 microgram.kg-1.min-1 iv) also
significantly decreased PRA. These data indicate that when
beta-adrenoceptors are blocked by propranolol, tonic neural stimulation of
renin secretion is mediated by renal alpha-adrenoceptors.
