T he cytochrome P450 system transforms AA to hydroxyeicosatetraenoic acid (HETE) metabolites that are vasoactive and affect transport in several nephron segments. A principal product of this system, 20-HETE, participates in key mechanisms that regulate the renal circulation and extracellular fluid volume. We hypothesized that excess production of 20-HETE, which constricts the renal vasculature, contributes to the renal functional disturbances in patients with hepatic cirrhosis, particularly the depression of renal hemodynamics. The development of a precise and sensitive gas chromatographic/mass spectrometric method makes it possible to measure 20-HETE and the subterminal HETEs (16-,17-,18-, and 19-HETEs) in biological fluids. As 20-HETE was excreted as the glucuronide conjugate, measurement of 20-HETE required treatment of urine with glucuronidase. We measured HETEs in the urine of patients with cirrhosis, and compared these values to those of normal subjects. Urinary excretion rate of 20-HETE was highest in patients with ascites; 12.5+/-3.2 ng/min vs. 5.0+/-1.5 and 1.6+/-0.2 ng/min in cirrhotic patients without ascites and in normal subjects, respectively. Excretion of 16-, 17-, and 18-HETEs was not increased. In patients with cirrhosis, the excretory rate of 20-HETE was several-fold higher than those of prostaglandins and thromboxane, whereas in normal subjects 20-HETE and prostaglandins were excreted at similar rates. Of the eicosanoids, only increased excretion of 20-HETE in subjects with cirrhosis was correlated (r = -0.61; P < 0.01) with reduction of renal plasma flow (RPF).