Selective Renal Dopamine-1 Receptor Stimulation in Man

Abstract

The selective dopamine-1 (DA-1) receptor agonist, fenoldopam, was studied during intravenous administration to ten normal male subjects on a diet of 150 mEq sodium and 60 mEq potassium per day to determine the mechanism of dopamine-induced natriuresis. During DA-1 receptor stimulation, urine flow rate and renal plasma flow manifested a biphasic increase. Urine flow rate increased from a control of 13 ± 1 to 17 ± 1.2 ml/min and again to a peak of 16 ± 1. Renal plasma flow increased from 344 ± 39 to 481 ± 44 ml/min and then to 497 ± 38. Sodium excretion (U_Na V) and fractional sodium excretion (FE_Na) demonstrated a sustained increase. U_Na V rose from a control of 0.21 ± 0.03 to 0.32 ± 0.05 mEq/min. FE_Na rose from a control of 1.6 ± 0.1 to 2.7 ± 0.6%. Fenoldopam did not alter glomerular filtraion rate.

The association of changes in renal plasma flow and in U_Na V and FE_Na demonstrate in man that DA-1 receptor stimulation causes natriuresis by direct renal tubular action. The renal tubular effect appears to be a major determinant of the degree of natriuresis.

Key Words:

• dopamine
• sodium metabolism
• natriuresis
• renal hemodynamics
• renal tubule