AJP - Endocrinology and Metabolism, Vol 244, Issue 1 37-E44, Copyright © 1983 by American Physiological Society
Stimulation of renin secretion by alpha-adrenoceptor agonists
M. L. Blair
This study was designed to determine whether stimulation of intrarenal
alpha-adrenoceptors can increase renin secretion rate (RSR) in the absence
of increased renal vascular resistance and to identify the accompanying
changes in renal function. Experiments were performed in
pentobarbital-anesthetized dogs in which renal perfusion pressure was
maintained at approximately 90 mmHg and the infused kidney was acutely
denervated. Renal artery infusion of the alpha-adrenoceptor agonist
methoxamine (0.5 microgram X kg-1 X min-1 for 30 min) increased RSR from
160 +/- 95 to 1,376 +/- 385 ng ANG I/min (P = 0.01) but did not decrease
renal blood flow (RBF); the same dose infused intravenously had no effect
on RSR or RBF. Intra-arterial phenylephrine infusion (0.5 microgram X kg-1
X min-1 for 9 min) increased RSR by 500 +/- 157 ng ANG I/min (P less than
0.01) and decreased both inulin clearance (Cin) and urinary sodium
excretion (UNaV) by 25% but did not affect RBF. At a lower concentration of
phenylephrine (0.2 microgram X kg-1 X min-1 for 9 min), RSR increased by
318 +/- 103 ng ANG I/min (P less than 0.01) and RBF, Cin, and UNaV did not
change. The increase in RSR was completely blocked by prazosin but was
unaffected by propranolol. In summary, renin secretion can be stimulated by
activation of intrarenal alpha-adrenoceptors even in the absence of
increased renal vascular resistance.
