A B S T R A C T The importance of renal perfusion pressure (RPP), the sympathetic beta adrenergic nervous system and renal prostaglandins (PG) on renin release during a uniform 15-17% reduction in blood pressure by hemorrhage (HH) was studied systematically in anesthetized dogs. All groups of animals had similar decrements in systemic and renal hemodynamics with HH. In control dogs (n = 7), both plasma renin activity (PRA, 4.1-9.0 ng angiotensin I/ml per h, P < 0.05) and renin secretory rate (RSR, 26-228 ng/ml per h min, P < 0.005) increased significantly with HH. This increase in renin release during HH was not abolished by any single maneuver alone including beta adre nergic blockade with d,l-propranolol (n = 6), renal PG inhibition with indomethacin (n = 7), or control of RPP (n = 6). However, when beta adrenergic blockade was combined with control of RPP (n = 7) during HH, neither PRA (1.9-2.7 ng/ml per h, NS) nor RSR (16-53 ng/ml per h min, NS) increased significantly. Similarly, a combination ofbeta adrenergic blockade and PG inhibition (n = 6) also abolished the increase in PRA (1.5-1.4 ng/ml per h, NS) and RSR (14-55 ng/ml per h*min, NS) 75216.