Studies of UDP-glucuronyltransferase activities in human liver microsomes

Human liver samples from a "liver bank" which have been previously characterized by the ability to catalyze cytochrome P-450 dependent reactions were analyzed for various UDP-glucuronyltransferase activities. When stored at -80 degrees C, UDP-glucuronyltransferase activities and latency characteristics of the enzyme appeared to be stable for up to 2 years. The correlation of UDP-glucuronyltransferase activity (4-methylumbelliferone as substrate) with enzyme activities towards 4-nitrophenol and 1-naphthol was much higher (r greater than 0.8) than that (r less than 0.3) observed with other enzyme activities (4-hydroxybiphenyl, morphine, and chloramphenicol as substrates), suggesting the presence of multiple enzyme forms in human liver. Livers of three patients treated with phenytoin or pentobarbital showed significantly higher UDP-glucuronyltransferase activities towards 1-naphthol, 4-methylumbelliferone, and bilirubin than those from five patients who did not receive these inducing agents.