ROLE OF PERIPHERAL ADRENORECEPTORS AND VASOPRESSIN IN THE SUPPRESSION OF PLASMA-RENIN ACTIVITY BY L-DOPA IN CARBIDOPA-TREATED DOGS

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 210  (3) , 368-372
Abstract
When extracerebral dopa decarboxylase is inhibited by carbidopa [CDP], L-dopa [L-DP] lowers plasma renin activity (PRA). The present study was designed to determine whether this suppression of PRA is mediated by the sympathetic nerves, and to identify the peripheral adrenergic receptor types involved. All experiments were performed in pentobarbital-anesthetized dogs in which changes in renal perfusion pressure were minimized by a suprarenal aortic clamp. Neither .alpha. adrenoreceptor blockade with phenoxybenzamine nor .beta. adrenoreceptor blockade with propranolol was by itself sufficient to block the suppression of PRA by L-dopa with carbidopa. Combined .alpha. and .beta. adrenoreceptor blockade lowered PRA by L-DP with carbidopa. Phenoxybenzamine decreased PRA by 48% when administered to propranolol-treated animals. These data indicate that L-DP with CDP suppresses PRA by decreasing sympathetic nerve stimulation of both .alpha. and .beta. adrenoreceptors. Plasma vasopressin concentration was significantly decreased by L-DP with CDP both in the control group and in animals with combined .alpha. and .beta. adrenoreceptor blockade. Because plasma vasopressin levels decreased after L-DP, vasopressin is unlikely to play a causative role in the suppression of PRA.