Influence of renal perfusion pressure on alpha- and beta-adrenergic stimulation of renin release.

Experiments were performed in pentobarbital-anesthetized dogs to 1) determine if neural stimulation of renin release can be mediated by renal alpha-adrenoceptors at renal nerve stimulation (RNS) frequencies that have little or no effect on total renal blood flow (less than or equal to 1.2 Hz) and 2) ascertain whether alpha-adrenergic control of renin release is affected by renal perfusion pressure (RPP). The renal nerves were electrically stimulated both in the absence of RPP control and with RPP controlled near 85 mmHg. Decreased RPP lowered the threshold for neurogenic stimulation of renin release from less than or equal to 1.2 to 0.3 Hz. beta-Adrenoceptor blockade with propranolol blunted the renin secretion rate (RSR) response to graded RNS (0.3-5.0 Hz), but the extent of inhibition during low-frequency RNS was dependent on RPP. Propranolol prevented increased RSR at 0.6-1.2 Hz RNS when RPP was 111-120 mmHg but not when RPP was 85 mmHg. Combined alpha- and beta-blockade with prazosin and propranolol totally prevented increased RSR during 0.6-1.2 Hz RNS at reduced RPP. In summary, both alpha- and beta-adrenoceptors mediate neural stimulation of renin release at RNS frequencies that do not decrease total renal blood flow when RPP is 85 mmHg.