The effect in man of (+)-propranolol and racemic propranolol on renin secretion stimulated by orthostatic stress.

Renin secretion is enhanced by stimulation of the sympathetic nervous system, as seen in haemorrhage, the upright posture and renal nerve stimulation; it is also enhanced by infusion of catecholamines pander, 1967). Propranolol has been shown to reduce renin secretion following sympathetic stimuli in man (Winer, Chokshi, Yoon & Freedman, 1969) and dogs (Assaykeen, Clayton, Goldfien & Ganong, 1970). This effect of the drug is attributed to its beta-adrenergic antagonist action. However, propranolol which is available for ordinary therapeutic purposes, is a racemic mixture of (+)and (-)-propranolol, and has membrane stabilizing (local anaesthetic) properties in addition to its beta-blocking effect. The individual isomers have approximately equal membrane-stabilizing potency, but the (+) form (R absolute configuration, Dukes & Smith, 1971) has only 1-2% of the beta-adrenergic antagonist potency of the (-) form (Barrett & Cullum, 1968). Further, Winer, Chokshi 8z Walkenhorst (1971) reported that the (+) and (-) isomers are equally effective in blocking isoprenaline-induced renin secretion in dogs. To find out if the action of propranolol on renin secretion is due to its beta-adrenergic blocking properties, plasma renin activities (PRA) were measured in subjects submitted to orthostatic stress, preceded on separate occasions by racemic propranolol or (+)-propranolol. A summary of the material of this paper has already appeared (Tobert, Slater, Fogelman, Lightman, Kurtz & Payne, 1972).