Urinary dopamine excretion and renal responses to fenoldopam infusion in blacks and whites.

Dopamine is an endogenous natriuretic amine that contributes to the maintenance of sodium homeostasis. Deficiencies in the renal production of dopamine and the action of dopamine on renal tubular receptors have been observed in human hypertension and may contribute to salt sensitivity of blood pressure. Ethnic differences in the sodium-to-dopamine relationship may contribute to the higher prevalence of salt sensitivity in blacks. The authors assessed dopaminergic activity in two studies. In the first, daytime and nighttime excretion of sodium and dopamine were compared in 11 black and 17 white normotensive patients. No racial difference in the rate of sodium or dopamine excretion during either period was observed. In the second study, a graded infusion of the dopamine-1 receptor agonist, fenoldopam, was performed in 14 black and 17 white normotensive patients. There was no racial difference in the natriuretic responses. Previously described lower rates of renal free water clearance and potassium excretion in blacks compared with whites were maintained during fenoldopam infusion, suggesting that dopamine is not a mediator of those differences. The authors conclude that there are no race-related differences in dopamine excretion or activity in normotensive patients.