Differential stability of drug-metabolizing enzyme activities in primary rat hepatocytes, cultured in the absence or presence of dexamethasone

Joellyn M. McMillan, Joseph G. Shaddock, Daniel A. Casciano, Michael P. Arlotto, Julian E.A. Leakey

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41 Scopus citations

Abstract

The effects of primary hepatocyte culture on the rat cytochrome P450-dependent monooxygenase system and several conjugating enzyme activities were examined using a culture system similar to those used for evaluation of chemicals as potential genotoxins. Cytochrome P450 and cytochrome b5 contents progressively decreased throughout the 72-h culture period to < 25% of initial values, whereas cytochrome P450 reductase rapidly decreased by 50% during attachment, but then remained stable. Cytochrome P450-dependent testosterone hydroxylase activities decreased more rapidly in culture than did cytochrome P450 content reaching < 50% of attachment levels by 24 h. Cytochrome P450IIIA immunoreactive protein decreased at a similar rate to testosterone-6β-hydroxylase. Activated UDP-glucuronyltransferase activities towards 1-naphthol and testosterone declined more slowly over the 72 h than cytochrome P450 and remained at 50-60% of initial values at 72 h. UDP-glucuronyltransferase activity towards digitoxigenin monodigitoxoside (DIG) did not decrease during culture. Glutathione-S-ransferase and sulfotransferase activities also declined during the 72 h at rates which appeared to be isozyme-dependent. Addition of 1 μM dexamethasone (DEX) to the culture medium increased UDP-glucuronyltransferase activity towards DIG, cytochrome P450 reductase and testosterone-6β-hydroxylase activities up to 2.5-, 2.0- and 7-fold, respectively and induced cytochrome P450IIIA immunoreactive protein(s) in the hepatocytes after 24 and 48 h of culture; DEX was less effective at the 72 h time-point. DEX treatment also significantly accelerated the decreases in glutathione-S-transferase activities and in sulfotransferase activities towards 1-naphthol and estrone. Thus, it appears that primary rat hepatocytes cultured under standard conditions, not only rapidly lose their monooxygenase capabilities, but also some of their capacity for conjugation.

Original languageEnglish (US)
Pages (from-to)81-92
Number of pages12
JournalMutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
Volume249
Issue number1
DOIs
Publication statusPublished - Jul 1991

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Keywords

  • Dexamethasone
  • Drug-metabolizing enzymes
  • Hepatocyte culture
  • Monooxygenase, cytochrome P450-dependent

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Health, Toxicology and Mutagenesis

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