Different effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on glucuronide conjugation of various aglycones. Studies in Wistar and Gunn rats.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) (20 μg/kg) was administered to homozygous Gunn and Wistar as well as heterozygous rats, and the activity of UDP-glucuronosyltransferase determined in the liver and kidney toward o-aminophenol, p-nitrophenol, 4-methylumbelliferone, and bilirubin. Diethylnitrosamine was used to activate the enzyme in vitro. TCDD did not enhance UDP-glucuronosyltransferase (UDPGT) activity in the Gunn rat, either in the liver or in the kidney. In the Wistar rat, the UDPGT activity toward methylumbelliferone was enhanced eightfold in the liver and twofold in the kidney. TCDD did not affect UDPGT activity toward bilirubin. Diethylnitrosamine activated o-aminophenol and p-nitrophenol glucuronidation in vitro in the liver only. No activation in vitro due to diethylnitrosamine treatment could be seen in the liver of the TCDD-treated Wistar rat.