title: Insulin suppresses the induction of CYP2B1 and CYP2B2 gene expression by phenobarbital in adult rat cultured hepatocytes.
abstract: The effect of insulin on the phenobarbital (PB)-induced gene expression of CYP2B1 and CYP2B2 (CYP2B1/2B2) in adult rat hepatocytes was investigated. Insulin, which has been regarded as an essential hormone for primary hepatocytes, was found to strongly suppress the induction of CYP2B1/2B2 gene expression in hepatocytes cultured on EHS-gel. Although the induction by PB was not seen in monolayer hepatocytes cultured on type I collagen under standard culture conditions, the induced expression of the CYP2B1/2B2 gene was observed in monolayer hepatocytes by removing insulin from the medium. Further, we succeeded in maintaining the prolonged induction of CYP2B1/2B2 by PB in monolayer hepatocytes by using a medium containing dexamethasone but not insulin. Since the PB-induced UDP-glucuronosyltransferase gene expression was not reduced by insulin, the suppressive effect of insulin was considered to be specific to the CYP2B1/2B2 gene. These results demonstrate that insulin in media masks the PB-induced expression of the CYP2B1/2B2 gene in conventional monolayer hepatocytes and that the use of insulin-free media with primary hepatocytes provides a useful tool for investigating the molecular mechanism of CYP2B1/2B2 gene expression.
authors.affiliation: Department of Applied Biological Sciences, Nagoya University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshida
authors.forename: N
authors.initials: N
authors.lastname: Kimura
authors.forename: H
authors.initials: H
authors.lastname: Oda
authors.forename: A
authors.initials: A
authors.lastname: Kakinuma
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D002478:Cells, Cultured; D046508:Culture Techniques / Q000379:methods; D019362:Cytochrome P-450 CYP2B1 / Q000187:drug effects*; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects*; D003921:Diabetes Mellitus, Experimental; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D015971:Gene Expression Regulation, Enzymologic; D007328:Insulin / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D010634:Phenobarbital / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013250:Steroid Hydroxylases / Q000187:drug effects*; D013311:Streptozocin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D007328:Insulin; D013311:Streptozocin; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; D019362:Cytochrome P-450 CYP2B1; C025619:steroid 16-beta-hydroxylase; D010634:Phenobarbital