[Effect of hypotensive preparations on humoral factors in blood circulation regulation].

A total of 178 patients with labile arterial hypertension were examined for the effect of propranolol and clonidine on the central hemodynamics, plasma renin, dopamine- beta-hydroxylase, urine kallikrein, and blood prekallikrein and kallikrein. The results suggest that basic to changes in the hemodynamics produced by a single administration of propranolol is its beta-adrenoblocking effect proper. The decrease in the general peripheral resistance due to prolonged propranolol therapy may be determined by activation of the blood kallikrein-kinin system and enhancement of the descending inhibition of the sympathetic nervous system because of activation of the central alpha-adrenoreceptors under long-term blockade of beta-adrenoreceptors of the central nervous system. The changes in the hemodynamics produced by low doses of clonidine may be accounted for by its central alpha-adrenomimetic effect.