title: Transient expression of CYP1A1 in rat epithelial cells cultured in suspension.
abstract: Suspension of human epidermal cells in methylcellulose-containing medium induces CYP1A1 by a mechanism requiring functional Ah receptor (AhR). In present work CYP1A1 mRNA was induced in a variety of cultured rat epithelial cells by suspension, but the induction was transient, with CYP1A1 mRNA reaching maximal levels by 5 h and disappearing by 12 h. Though the methylcellulose itself contained no detectable ligand, (a) suspension activated the AhR, as judged by mobility shift assays, (b) the AhR competitive inhibitor alpha-naphthoflavone inhibited suspension-mediated induction, and (c) induction was dependent upon dioxin responsive transcriptional elements in the CYP1A1 promoter. The rapid disappearance of CYP1A1 mRNA after 5 h of suspension was unaffected by the addition of TCDD but was prevented by the inclusion of the protein synthesis inhibitor cycloheximide. Thus the downregulation appears to be mediated by a novel short-lived protein induced or activated by suspension.
authors.affiliation: Department of Environmental Toxicology, University of California, One Shields Avenue, Davis, California 95616-8588, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Monk
authors.forename: M S
authors.initials: MS
authors.lastname: Denison
authors.forename: R H
authors.initials: RH
authors.lastname: Rice
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003470:Culture Media; D003513:Cycloheximide / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism; D008747:Methylcellulose; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D003470:Culture Media; D017931:DNA Primers; D000072317:Polychlorinated Dibenzodioxins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D008747:Methylcellulose; D003513:Cycloheximide; D019363:Cytochrome P-450 CYP1A1