alpha-Adrenoceptor-mediated inhibitory effect of the sympathetic nervous system on the isoprenaline-induced increase in plasma renin concentration.

The importance of the sympatho-adrenal system for the isoprenaline-induced increase in plasma renin concentration was investigated in conscious rats Ganglionic blockade by trimethidinium (10 mg kg-1) increased the dose-dependent elevation of plasma renin concentration induced by isoprenaline (0.03-0.48 microgram kg-1 min-1). Also treatment of the rats with guanethidine (6 mg kg-1) or reserpine (2.5 mg kg-1, given 16 and 7 h prior to the experiments) further increased the effect of isoprenaline (0.5 microgram kg-1 min-1) on plasma renin concentration. Unilateral renal denervation combined with contralateral nephrectomy doubled the effect of the beta-sympathomimetic amine on renin release. The alpha-adrenoceptor antagonist phenoxy-benzamine (3 mg kg-1) also enhanced the effect of isoprenaline on this parameter. It is concluded that apart from a stimulation of renin release via beta-adrenoceptors the sympathetic nervous system may inhibit renin release via stimulation of alpha-adrenoceptors.