Biphasic regulation of cytochrome P450 2B1/2 mRNA expression by dexamethasone in primary cultures of adult rat hepatocytes maintained on matrigel

Biochem Pharmacol. 1994 Nov 1;48(9):1815-22. doi: 10.1016/0006-2952(94)90468-5.


We have demonstrated recently that although rat hepatocytes rapidly lose their cytochrome P450 mRNA content following their introduction into primary culture, hepatocytes cultured on Matrigel, a reconstituted basement membrane, subsequently spontaneously "reexpress" the mRNAs of some constitutive P450 forms (Kocarek et al., Mol Pharmacol 43: 328-334, 1993). In the present study, we used the Matrigel cell culture system to examine the dose-dependent effects of dexamethasone (DEX) treatments on the mRNAs for two of the P450 forms that are reexpressed spontaneously between days 3 and 5 in culture, 2B1/2 and 2C6. Treatment of cultured hepatocytes with low doses of DEX (10(-9) to 10(-8) M) that induced the mRNA for tyrosine aminotransferase, a model glucocorticoid-inducible gene, suppressed the spontaneous appearance of 2B1/2 mRNA while having little or no effect on the level of 2C6 mRNA or on beta-actin mRNA. However, treatment of the hepatocyte cultures with high doses of DEX (10(-6) to 10(-5) M) that induced P450 3A1 mRNA increased the amounts of the 2B1/2 and 2C6 mRNAs (4.1- and 2.4-fold, respectively, at 10(-5) M DEX). In contrast to the suppressive effects on the spontaneous increases in 2B1/2 mRNA, low doses of DEX (10(-8) to 10(-7) M) enhanced the induction of 2B1/2 mRNA by phenobarbital (2.5-fold at 10(-7) M DEX). Treatment of the hepatocyte cultures with triamcinolone acetonide, another potent glucocorticoid, suppressed spontaneous 2B1/2 mRNA expression at low doses, but did not induce 2B1/2 mRNA at high doses. Treatments with steroids of other classes, including dihydrotestosterone, 17 alpha-ethinylestradiol, fludrocortisone or R-5020, failed to suppress 2B1/2 mRNA levels at low doses. Additionally, treatment with RU-486, a glucocorticoid/progestin receptor antagonist, induced 2B1/2 mRNA at high doses (10(-6) to 10(-5) M). The suppressive effects of DEX on spontaneous 2B1/2 mRNA expression observed at low doses are consistent with a classical glucocorticoid-mediated mechanism, while the high-dose inductive effects of DEX appear to be exerted through a nonclassical mechanism, perhaps akin to that for induction of 3A1.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Aryl Hydrocarbon Hydroxylases*
  • Cells, Cultured
  • Collagen*
  • Cytochrome P-450 Enzyme System / biosynthesis
  • Cytochrome P-450 Enzyme System / genetics*
  • Dexamethasone / pharmacology*
  • Dose-Response Relationship, Drug
  • Down-Regulation
  • Drug Combinations
  • Enzyme Induction
  • Gene Expression Regulation, Enzymologic
  • Laminin*
  • Liver / drug effects*
  • Liver / enzymology
  • Proteoglycans*
  • RNA, Messenger / analysis*
  • Rats
  • Steroid Hydroxylases / biosynthesis
  • Steroid Hydroxylases / genetics*


  • Drug Combinations
  • Laminin
  • Proteoglycans
  • RNA, Messenger
  • matrigel
  • Dexamethasone
  • Collagen
  • Cytochrome P-450 Enzyme System
  • Steroid Hydroxylases
  • Aryl Hydrocarbon Hydroxylases
  • steroid 16-beta-hydroxylase