The hepatorenal syndrome (HRS) is characterized by renal vasoconstriction leading to deterioration of renal function in patients with liver disease. A possible role of endothelin-1 (ET-1) in the pathogenesis of HRS has been suggested, but a correlation between ET-1 plasma levels and the development of HRS as well as the recovery from HRS following OLT has not been shown yet. We performed longitudinal measurements of ET-1 plasma levels in four groups of patients, 5 patients with HRS before and after orthotopic liver transplantation (OLT), 10 patients without HRS undergoing OLT, 20 patients with chronic renal failure but without liver disease, and 12 healthy controls. Before OLT, plasma levels of ET-1 were higher in patients with HRS (19.5 +/- 8.6 ng/l, P < 0.001; n = 5) compared to patients without HRS (4.9 +/- 1.1 ng/l; n = 10), normals (1.2 +/- 0.18 ng/l; n = 12), and patients with chronic renal failure (2.4 +/- 0.4 ng/l; n = 20). Patients with HRS compared to patients without HRS had higher levels for creatinine (2.42 +/- 0.6 vs. 0.89 +/- 0.05 mg/dl, P < 0.05), creatinine clearance (107 +/- 9 ml/min vs. 44.6 +/- 5.5 ml/ min, P < 0.001), and bilirubin (11.4 +/- 3.8 vs. 3.7 +/- 1 mg/dl, P < 0.05) before OLT. Within one week after OLT, there was a rapid decrease in ET-1 levels in patients with HRS while creatinine and bilirubin levels decreased slower. Regression analysis revealed a weak correlation between serum creatinine and ET-1 (r = 0.192, P = 0.04) and a significant correlation between serum bilirubin and ET-1 (r = 0.395, P < 0.001). The means of the ET-1 levels decreases rapidly with improvement of liver function after OLT. Levels of ET-1 correlate with excretory liver function assessed by bilirubin. The fall in ET-1 levels preceding improvement of renal function further strengthens the concept of ET-1 being a causative factor in HRS.