Differential induction of cytochrome P-450-dependent monooxygenase, epoxide hydrolase, glutathione transferase and UDP glucuronosyl transferase activities in the liver of the rainbow trout by beta-naphthoflavone or Clophen A50.
After administration of beta-naphthoflavone and Clophen A50 to juvenile rainbow trout, activities of hepatic cytochrome P-450-dependent deethylation of 7-ethoxyresorufin was increased 172- and 49-fold, respectively. Glutathione transferase activity towards 1-chloro 2,4 dinitrobenzene and UDP glucuronosyltransferase activities towards p-nitrophenol, 1-naphthol and testosterone were increased 1.4 to 3.0-fold by beta-naphthoflavone or Clophen A50. However, significant increases of the rate of glucuronidation of 1-naphthol by Clophen A50 and of testosterone by both Clophen A50 and beta-naphthoflavone were only determined when the activities were measured in digitonin activated microsomes. Epoxide hydrolase activity was not affected by beta-naphthoflavone or Clophen A50. The time course of induction of the various xenobiotic metabolizing enzymes exhibited different patterns. 7-Ethoxyresorufin-O-deethylase activity reached peak values 3 and 7 days after the administration of beta-naphthoflavone and Clophen A50, respectively. The rate of induction of glutathione transferase activity and UDP glucuronosyltransferase activities towards p-nitrophenol and 1-naphthol were relatively slow and did not reach distinct peak levels. These activities were still on maximum levels 4-6 weeks after the treatment. Glucuronidation of testosterone reached peak values 1 week after treatment with both beta-naphthoflavone and Clophen A50. The dissimilar patterns of induction of the cytochrome P-450-dependent activities and the various conjugation activities may indicate that these xenobiotic metabolizing enzymes are differently regulated in the rainbow trout liver.
D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System; D004072:Digitonin / Q000494:pharmacology; D004790:Enzyme Induction; D004851:Epoxide Hydrolases / Q000096:biosynthesis*; D005419:Flavonoids / Q000494:pharmacology*; D014453:Glucuronosyltransferase / Q000096:biosynthesis*; D005982:Glutathione Transferase / Q000096:biosynthesis*; D007700:Kinetics; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D010105:Oxygenases / Q000096:biosynthesis*; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D013379:Substrate Specificity; D014337:Trout; D019324:beta-Naphthoflavone
D001571:Benzoflavones; D005419:Flavonoids; D019324:beta-Naphthoflavone; C025647:clophen A50; D003577:Cytochrome P-450 Enzyme System; D011078:Polychlorinated Biphenyls; D010105:Oxygenases; D014453:Glucuronosyltransferase; D005982:Glutathione Transferase; D004851:Epoxide Hydrolases; D004072:Digitonin