Transient expression of CYP1A1 in rat epithelial cells cultured in suspension

Arch Biochem Biophys. 2001 Sep 1;393(1):154-62. doi: 10.1006/abbi.2001.2475.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Cells, Cultured
  • Culture Media
  • Cycloheximide / pharmacology
  • Cytochrome P-450 CYP1A1 / genetics*
  • DNA Primers / genetics
  • Gene Expression / drug effects
  • Genes, Reporter
  • Keratinocytes / drug effects
  • Keratinocytes / metabolism
  • Methylcellulose
  • Polychlorinated Dibenzodioxins / pharmacology
  • Promoter Regions, Genetic
  • Protein Synthesis Inhibitors / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Rats
  • Receptors, Aryl Hydrocarbon / antagonists & inhibitors
  • Receptors, Aryl Hydrocarbon / metabolism


  • Culture Media
  • DNA Primers
  • Polychlorinated Dibenzodioxins
  • Protein Synthesis Inhibitors
  • RNA, Messenger
  • Receptors, Aryl Hydrocarbon
  • Methylcellulose
  • Cycloheximide
  • Cytochrome P-450 CYP1A1