RESUMO
Suppression of renin release by beta-adrenoceptor blocking drugs has been advocated as the prime blood pressure lowering mechanism of these agents. The present report casts doubt on this proposition in three ways. In the first study, involving 22 patients with borderline hypertension, patients with elevated plasma renin levels showed normalization of the blood pressure after pharmacological autonomic blockade with intravenous atropine, propranolol and phentolamine, the time course of the pressure fall being such as to exclude suppression of renin release as the antihypertensive mechanism. It is clear that in patients with mild hypertension and high plasma renin levels, the elevation of blood pressure is maintained by a neurogenic mechanism, the elevated plasma renin having no direct role in sustaining the higher blood pressure. In two additional studies involving 21 patients in all with mild to moderately severe essential hypertension, to whom propranolol was administereed by mouth for 1--3 months, two findings were of interest:1) patients with low-renin essential hypertension showed a good antihypertensive response to propranolol, and 2) in some patients a dosedependent dissociation of the renin and blood pressure lowering action of propranolol could be demonstrated. These findings militate against the assumption that propranolol selectively lowers the blood pressure in "renin-dependent" hypertension, and strongly suggest that the antihypertensive action of this drug is not mediated by depression of plasma renin activity.
