Neurohormonal activation, the renal dopaminergic system and sodium handling in patients with severe heart failure under vasodilator therapy

The benefits of tailoring therapy with vasodilators in patients with severe heart failure are well documented, but this may lead to neurohormonal activation and sodium retention. Renal dopamine has local natriuretic actions and interacts with other hormones involved in renal sodium handling. The aim of the present work was to determine the effects of arterial underfilling induced by vasodilator therapy on renal sodium handling, neurohormonal activation and the activity of the renal dopaminergic system in patients with severe heart failure. For this purpose we monitored haemodynamic parameters, plasma levels of type B natriuretic peptide (BNP), catecholamines, aldosterone, renin activity (PRA), sodium and creatinine, and urinary excretion of sodium, creatinine, l-DOPA, dopamine and its metabolites, before initiation of sodium nitroprusside therapy and every 6 h thereafter (for 42 h), and again after 5 days of angiotensin-converting enzyme (ACE) inhibition, in 10 male patients with severe heart failure. The results of nitroprusside therapy were a marked increase in cardiac index and a substantial decrease in systemic vascular resistance index. Plasma levels of BNP decreased significantly, while PRA, noradrenaline and aldosterone showed marked increases, resulting in a substantial reduction in urinary sodium excretion. Creatinine clearance was not affected. Urinary dopamine and dopamine metabolites increased in response to nitroprusside therapy. After 5 days of ACE inhibition, urinary sodium returned to baseline values, while urinary dopamine was markedly reduced. These results suggest that the renal dopaminergic system is activated in patients with severe heart failure by stimuli leading to sodium renal reabsorption.