[The influence of propranolol, practolol and theophylline on the plasma renin activity (author's transl)].

The stimulating effect of theophylline on the plasma renin activity (PRA) under beta-receptor blockade by propranolol or practolol was investigated in 27 patients with essential hypertension of degree I-II. After propranolol and also practolol PRA decreased about thirty per cent of the basal value, increased however by the factor of 2 to 3 after application of theophylline, in spite of the blockade of the beta-receptors indicated by a slight decrease of systolic blood pressure and heart rate. The effect of propranolol and practolol on the basal PRA was not different. Our results show the possibility, to stimulate renin secretion despite blockade of beta receptors by propranolol or practolol, respectively.