Characterization of Microsomal Bilirubin and p-Nitrophenol Uridine Diphosphate Glucuronosyltransferase Activities in Human Liver: A Comparison with Rat Liver

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Abstract
The bilirubin and p-nitrophenol uridine diphosphate glucuronosyltransferase (UDP-GT) activities have been characterized from human liver microsomes and compared to those from rat liver. This study was performed on large samples of human liver obtained from 20 organ donors. The kinetic constants as well as sensitivities to digitonin, temperature, pH and diethylnitrosamine were determined. Our results suggest that UDP-GT activities have characteristics different in human and rat liver microsomal membranes. Moreover, differences in digitonin-induced activation, in thermodenaturation and in the response to diethylnitrosamine were found between bilirubin and p-nitrophenol UDP-GT activities. This supports the hypothesis of the probable heterogeneity of UDP-GT.