Comparative effects of dopaminergic agonists on cardiovascular, renal, and renin-angiotensin systems in hypertensive patients.

The role of dopaminergic receptors on renal function has been extensively studied. Recently dopaminergic receptor has been classified in two subtypes D1 and D2, which seem to have different modulatory function. However, the role of dopaminergic receptors on cardiovascular function and more specifically the potential role of dopaminergic agonists as antihypertensive agents has not yet been clarified. Nine outpatients with mild and moderate hypertension were studied in the Cardiology Service of Vargas Hospital with a D1 agonist, piribedil, at 50-100 mg/day, orally, for 8 weeks, and with a D2 agonist, bromocriptine, at 2.5 - 5 mg/day, orally, for an another 8 weeks by using a placebo comparative crossover design. Piribedil reduced blood pressure with a modest increase in heart rate, plasma renin activity, and of plasma aldosterone, and an important increment of renal function. Bromocriptine reduced blood pressure with a decrease in heart rate and plasma aldosterone without altering renal function. There was no orthostatic hypotension with either agent. The authors conclude that activation of dopaminergic D1 receptor induces a vasodilatory and antihypertensive effect with a reflex increase in sympathetic tone, whereas activation of dopaminergic D2 receptor induces a decrease in sympathetic tone, probably due to a decrease in norepinephrine release at adrenergic endings. The potential effect of these compounds as antihypertensive agents is of great interest because blood pressure reduction can be induced by a new mechanism, i.e. activation of dopaminergic receptors which results in a decrease of the renin angiotensin system or a vasodilatory action.(ABSTRACT TRUNCATED AT 250 WORDS)