title: Phase I and phase II xenobiotic biotransformation in cultures and co-cultures of adult rat hepatocytes.
abstract: The aim of this study was to measure the activity of phase I and II key enzymes in the biotransformation of xenobiotics and their inducibility by phenobarbital (2 mM) in two currently used in vitro models, namely adult rat hepatocytes, conventionally cultured or co-cultured with rat epithelial cells derived from primitive biliary duct cells. For phase I, the cytochrome P450 content and the enzymic activities of 7-ethoxycoumarin O-deethylase and aldrin epoxidase have been determined, for phase II glutathione S-transferase activity was measured. In conventional cultures, all phase I parameters investigated declined continuously as a function of culture time. Two mM phenobarbital had inducing effects on 7-ethoxycoumarin O-deethylase and glutathione S-transferases but not on aldrin epoxidase. In co-cultures, after an initial decrease, a steady state situation developed for all the parameters measured, lasting for at least 10 days. The cytochrome P450 content, the 7-ethoxycoumarin O-deethylase, aldrin epoxidase and glutathione S-transferase activities were maintained from 3 to 4 days on at 25, 100, 15 and 50%, respectively, of their corresponding value obtained for freshly isolated hepatocytes. After phenobarbital treatment, the parameters mentioned were significantly increased with the exception of the aldrin epoxidase activity of which the inducibility was nearly completely lost.
authors.affiliation: Department of Toxicology, Vrije Universiteit Brussel, Belgium.
authors.forename: V
authors.initials: V
authors.lastname: Rogiers
authors.forename: Y
authors.initials: Y
authors.lastname: Vandenberghe
authors.forename: A
authors.initials: A
authors.lastname: Callaerts
authors.forename: G
authors.initials: G
authors.lastname: Verleye
authors.forename: M
authors.initials: M
authors.lastname: Cornet
authors.forename: K
authors.initials: K
authors.lastname: Mertens
authors.forename: W
authors.initials: W
authors.lastname: Sonck
authors.forename: A
authors.initials: A
authors.lastname: Vercruysse
mesh_terms: D015660:7-Alkoxycoumarin O-Dealkylase / Q000096:biosynthesis; D000818:Animals; D001711:Biotransformation; D002478:Cells, Cultured / Q000187:drug effects; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis; D004790:Enzyme Induction / Q000187:drug effects; D005982:Glutathione Transferase / Q000096:biosynthesis; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000096:biosynthesis; D008954:Models, Biological; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats
chemical_list: D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C019647:aldrin epoxidase; D015660:7-Alkoxycoumarin O-Dealkylase; D005982:Glutathione Transferase; D010634:Phenobarbital