BETA-ADRENERGIC CONTROL OF RENIN IN SODIUM-DEPRIVED CONSCIOUS DOGS - RENAL VERSUS EXTRARENAL LOCATION

This study was designed to determine if tonic beta-adrenergic control of plasma renin activity (PRA) during dietary sodium restriction is du e to stimulation of renal beta-adrenoceptors, extrarenal beta-adrenoce ptors, or both. Experiments were performed in six conscious resting un inephrectomized dogs with chronically indwelling catheters in the aort a, vena cava, and remaining renal artery. The dogs were fed a low-sodi um diet of approximately 7 mequiv. Na/day. PRA decreased by 28 +/- 4% of control (p < 0.01) when the beta-adrenoceptor antagonist propranolo l was infused directly into the renal artery (ira) at a rate of 0.25 m u g . kg(-1). min(-1) for 45 min, whereas iv propranolol infusion at t he same rate had no effect on PRA. Propranolol infusion, 1 mu g . kg(- 1). min(-1) iv, decreased PRA by 22 +/- 8% of control (p < 0.05) and p roduced significantly greater systemic beta-adrenoceptor blockade but a similar renal plasma propranolol concentration as with ira infusion, 0.25 mu g . kg(-1). min(-1). Thus blockade of extrarenal beta-adrenoc eptors produced no additional suppression of PRA beyond that which cou ld be accounted for by blockade of renal beta-adrenoceptors. Therefore , suppression of PRA by propranolol is due solely to blockade of renal beta-adrenergic receptors in conscious sodium-deprived dogs.