BACKGROUND In patients with renal or cardiac failure, renal function may be endangered by elevated plasma concentrations of the vasoconstrictor endothelin-1 (ET-1). To mimic effects of pathologically increased plasma ET-1, we gave intravenous ET-1 in healthy subjects and examined whether simultaneous infusion of the ETA-receptor antagonist VML 588 would prevent the effects of ET-1 on the kidney. METHODS Nine healthy men received on four separate days intravenous infusion of ET-1 (2.5 ng/kg/min) superimposed on vehicle (saline) or on VML 588 infusion (0.05, 0.20 and 0.40 mg/kg/h) in randomized order to assess the effects on renal function and renal haemodynamics. RESULTS At resting plasma ET-1, infusion of VML 588 alone had no significant effects on renal function. Infusion of ET-1 alone decreased glomerular filtration rate by 11% and this reduction was not reversed by co-infusion of VML 588. ET-1 reduced renal blood flow by 35% and VML 588 reduced this decrease by one-third, in a dose-independent fashion. ET-1 increased the filtration fraction by 34% and VML 588 reduced this increase dose-independently by one-half. ET-1 increased renal vascular resistance by 59% and VML 588 reduced this increase dose-independently by one-half. Finally, ET-1 decreased sodium excretion by 58% and VML 588 reduced this decrease dose-independently by two-thirds. CONCLUSIONS ET-1-induced reductions in renal function were partially but not completely prevented in a dose-independent manner by the ETA-receptor antagonist VML 588.