title: Effect of 3-methylcholanthrene administration on expression of cytochrome P-450 isoforms induced by phenobarbital in rat hepatocytes.
abstract: The effects of an inducer on expression of cytochrome P-450 (P-450) isoforms induced antecedently by another inducer are unknown. Thus, we examined the amount of phenobarbital (PB)-inducible P-450 isoforms (P-450 2B1/2B2) in hepatocytes from rats injected first with PB and then with 3-methylcholanthrene (MC) (PB+MC-treated animals) by quantitative immunohistochemistry. In addition, expression of P-450 2B2 mRNA was examined by in situ hybridization. In PB-treated animals, P-450 2B1/2B2 content increased in perivenular and midzonal hepatocytes. In PB+MC-treated animals, however, the PB-induced increase in 2B1/2B2 content was suppressed in perivenular hepatocytes but promoted in midzonal hepatocytes. The hybridization signal for P-450 2B2 mRNA appeared almost exclusively in perivenular hepatocytes after 24 hr of PB injection and disappeared after 48 hr of injection. In PB+MC-treated animals, however, strong hybridization signal was observed in midzonal and perivenular hepatocytes after 48 hr of PB injection. The promotion of the increase in P-450 2B1/2B2 content in midzonal hepatocytes in PB+MC-treated animals probably corresponds to the strong hybridization signal, whereas there appeared to be a divergence between the intensity of the signal and the content in perivenular hepatocytes. The results indicate that MC administration drastically influences the pattern of expression of P-450 isoforms induced by PB in perivenular and midzonal hepatocytes.
authors.affiliation: Department of Anatomy, Kansai Medical University, Moriguchi, Osaka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Mino
authors.forename: J
authors.initials: J
authors.lastname: Watanabe
authors.forename: S
authors.initials: S
authors.lastname: Kanamura
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D015152:Blotting, Northern; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D019362:Cytochrome P-450 CYP2B1 / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology*; D008862:Microsomes, Liver / Q000276:immunology; D010634:Phenobarbital / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013250:Steroid Hydroxylases / Q000032:analysis / Q000276:immunology / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D019362:Cytochrome P-450 CYP2B1; C025619:steroid 16-beta-hydroxylase; D010634:Phenobarbital