AJP - Endocrinology and Metabolism, Vol 251, Issue 6 695-E702, Copyright © 1986 by American Physiological Society
Elevation of plasma renin activity by alpha-adrenoceptor agonists in conscious dogs
M. L. Blair, Y. H. Chen and H. Hisa
Experiments were performed in conscious trained dogs to determine whether
renal alpha-adrenergic receptors mediate stimulation or inhibition of renin
release. All dogs were uninephrectomized and surgically prepared with
chronically indwelling catheters in the aorta, vena cava, and remaining
renal artery at least 8 days before experiment. Direct renal artery (ia)
infusion of the alpha-adrenoceptor agonist phenylephrine, 0.25 or 0.50
microgram X kg-1 X min-1 for 30 min, increased plasma renin activity (PRA)
to 145 +/- 13 and 212 +/- 28% of control, respectively, within 5 min of
drug infusion (P less than 0.01) in conscious sodium-replete dogs. In
contrast, intravenous phenylephrine infusion decreased PRA by 50% (P less
than 0.001). The increase in PRA observed during ia phenylephrine infusion
was prevented by renal alpha-adrenoceptor blockade with phenoxybenzamine
but not by beta-adrenoceptor blockade with propranolol. Methoxamine,
another alpha-adrenoceptor agonist, also increased PRA when infused ia in
both sodium-replete dogs and in dogs maintained on a low-sodium diet. In
dogs with renal arterial electromagnetic flowprobes, ia phenylephrine
infusion increased PRA without decreasing total renal blood flow. In
summary, stimulation of renal alpha-adrenoceptors increases PRA in
conscious dogs. This stimulation can occur in the absence of significant
changes in total renal blood flow.
