/?-Adrenergic Stimulation

Isoproterenol infusion (0.1 /ig/kg per min) into the renal artery of the cat induced an increase in plasma renin concentration (PRC) from 14.3 ± 5.7 (mean ± SE) ng angiotensin I/ml per hr to 56.8 ± 7.7 after 70 minutes {P < 0.05) and an increase in catecholamine secretion rate from 38.7 ± 6.0 ng/kg per 10 min to 180.0 ± 40.0 after 70 minutes (P < 0.001). Intravenous infusion of the same dose of isoproterenol had no significant effect on adrenomedullary catecholamine secretion rate. Isoproterenol induced preferential norepinephrine release: the ratio of norepinephrine to epinephrine secretion changed from 11.5:23.7 during the control period to 130.0:40.1 70 minutes after the start of isoproterenol administration. Intrarenal infusion of propranolol (3.0 mg/kg per min) inhibited renal renin release and adrenal catecholamine secretion in response to intrarenal isoproterenol. Intravenous infusion (0.4 Mg/g P e r i) °f a n angiotensin II antagonist [Sar\ Ileu]angiotensin II abolished the catecholamine response to intrarenal isoproterenol infusion. It is suggested that intrarenal isoproterenol infusion stimulates renal renin release and angiotensin production which, in turn, stimulates a preferential secretion of adrenomedullary norepinephrine. Circ Res 47: 835-839, 1980