EFFECTS OF BETA ADRENERGIC BLOCKING AGENTS ON PLASMA RENIN ACTIVITY IN THE CONSCIOUS RABBIT

¹ Cardio-Renal Unit, Medical Research Department, Kanematsu Memorial Institute, Sydney Hospital, Sydney, Australia

The effects of propranolol, 1 mg/kg, oxprenolol, 1 mg/kg and prindolol, 0.125 mg/kg, given in separate experiments on blood pressure, heart rate and plasma renin activity (PRA) over a 3-hour period were investigated in three groups of conscious rabbits. Each of the beta blockers caused a significant fall in mean blood pressure, averaging 10 mm Hg. Heart rate fell after propranolol, but increased slightly after either of the other two drugs was given. Administration of propranolol or oxprenolol resulted in a significant fall in PRA to 50% of control values, whereas prindolol produced a progressive rise in PRA to almost 300% of the control value. Blood withdrawn for analysis was replaced by a protein-saline solution for, in control studies, it was shown that this procedure prevented the rise in PRA caused by blood sampling. In further control studies, propranolol, in the dose given, was shown to block isoproterenol-induced tachycardia in the rabbit. The differing effects of prindolol and the other two agents on PRA may reflect differences in their intrinsic sympathomimetic activity. The hypotensive effect of prindolol was clearly not due to suppression of the renin-angiotensin system. In a further group of 10 animals, when blood loss was not replaced by protein-saline, propranolol, 1 mg/kg, still resulted in a fall in PRA. Thus, propranolol lowered PRA both in the presence and absence of uncompensated blood loss.

This article has been cited by other articles:

				M. A. Weber, J. A. Lopez-Ovejero, J. I. Drayer, D. B. Case, and J. H. Laragh Renin Reactivity as a Determinant of Responsiveness to Antihypertensive Treatment Arch Intern Med, March 1, 1977; 137(3): 284 - 289. [Abstract] [PDF]