Inhibition of the renin--aldosterone axis and of prolactin secretion during pregnancy by L-dopa.

Recently, interactions between dopaminergic mechanisms and aldosterone secretion were described in non-pregnant subjects. The present study examined the effect of 1000 mg of L-dopa by mouth on plasma renin activity (PRA), and the concentrations of plasma aldosterone (PA) and prolactin (PRL) during normal pregnancy. Under basal conditions, there was a clear decrease of PRA, PA and PRL 60 min after oral intake of L-dopa in seven subjects; a further decrease was observed during the following 45 min, resulting in a total decrease of 41 (PRA), 44 (PA) and 56 (PRL) % of the respective arithmetic mean of the basal values. However, the response of PA to isopressor angiotensin II infusions was comparable before and shortly after treatment with L-dopa in 16 pregnant subjects. The decreased activity of the renin-aldosterone axis after administration of L-dopa may be attributed to an accumulation of dopamine and catecholamines in the brain, resulting in a diminution of sympathetic outflow from the central nervous system. The simultaneous and comparable changes of both PRA and PA after L-dopa treatment, as well as the reversibility of aldosterone suppression by infusion of angiotensin II, suggest that the inhibition of aldosterone secretion by L-dopa is mediated by a decrease of renin release.