Diuresis and natriuresis during continuous dopamine-1 receptor stimulation.

Stimulation of renal dopamine-1 (DA1) receptors for 3 hours produces an increase in renal plasma flow and sustained natriuresis. The present study was designed to assess the response of renal hemodynamic and tubular function to long-term DA1 receptor stimulation. Fenoldopam, a selective DA1 receptor agonist, was infused intravenously for 24 hours in 10 normal male subjects in metabolic balance at 150 mEq sodium and 60 mEq potassium intake in a single-blind, vehicle-controlled protocol. During DA1 receptor activation, urine flow rate and fractional excretion of sodium increased for the first 5 hours, 16.9 +/- 0.9 ml/min compared with a vehicle control value of 12.4 +/- 0.5 ml/min (p less than 0.001) and 2.0 +/- 0.1% compared with a vehicle control value of 1.1 +/- 0.1% (p less than 0.005), respectively. Urinary sodium excretion rose at 5 hours, 0.27 +/- 0.02 mEq/min compared with a vehicle control value of 0.14 +/- 0.01 mEq/min (p less than 0.01). Renal plasma flow increased during fenoldopam at 5 hours, 505 +/- 47 ml/min compared with a vehicle control value of 397 +/- 25 ml/min (p less than 0.01), and was sustained for 24 hours, 523 +/- 40 ml/min compared with 432 +/- 31 ml/min (p less than 0.05). The distal sodium load increased and the percentage of distal sodium reabsorption decreased during fenoldopam. Glomerular filtration rate, blood pressure, heart rate, plasma aldosterone concentration, plasma renin activity, and fractional excretion of potassium were unchanged. Selective DA1 receptor activation produced sustained 5-hour diuresis and 11-hour natriuresis without kaliuresis or a systemic hemodynamic effect.(ABSTRACT TRUNCATED AT 250 WORDS)