Patients with hepatic cirrhosis develop widespread abnormalities in kidney function and vasoactive hormones. These change rapidly after liver transplantation during immunosuppression with cyclosporine. The role of changing eicosanoid excretion and endothelin levels in regulating renal function after transplantation in humans remains uncertain. We studied 32 patients with regard to renal hemodynamics, glomerular filtration, urinary prostacyclin (6-keto-PG-F1-alpha), thromboxane (TBX2), and endothelin before and during the first four weeks after orthotopic liver transplantation. Arterial pressure rose from 106 +/- 2/61 +/- 2 to 146 +/- 4/81 +/- 2 mmHg, (P less than .001), while renal blood flow fell (686 +/- 38 to 453 +/- 24 ml/min/1.73 m2, P less than .05), as did GFR. Pretransplant excretion of 6-keto and TBX2 was above that of normal subjects and fell progressively after transplant, as did plasma renin activity and aldosterone. The 6-keto levels fell below normal after two weeks. The ratio of TBX2/6-keto remained elevated compared with normal subjects throughout the month after transplant (1.54 +/- 0.38 vs. 0.54 +/- 0.07, P less than .01). Endothelin levels rose during the first week (7.4 +/- 1.4 vs. 12.4 +/- 2.7 pg/ml, P less than .05), but fell back to baseline thereafter. These results indicate that high levels of urinary eicosanoids in patients with liver disease fall rapidly after liver transplantation during CsA immunosuppression. Unlike results in many experimental models, these data suggest that renal vasoconstriction in humans may be associated primarily with suppression in renal prostacyclin excretion rather than stimulation of thromboxane.