Apparent induction of microsomal carboxylesterase activities in tissues of clofibrate-fed mice and rats

Mohamed Bassem A Ashour, David E. Moody, Bruce D. Hammock

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23 Scopus citations


Treatment with 0.5% ( w w) dietary clofibrate, a peroxisome proliferator, for 14 days induced microsomal carboxylesterase activities for five substrates including malathion, clofibrate, diethylsuccinate, diethylphthalate, and p-nitrophenylacetate in liver and kidney of male Swiss-Webster mice and Sprague-Dawley rats. The induction was substrate, tissue, and species dependent. The carboxylesterase activity was induced in mouse from 1.2- to 2.2-fold (liver) and from 1.1- to 1.7-fold (kidney) depending upon substrate used. Analogous values from rat ranged from 1.0- to 1.4-fold (liver) and from 1.1- to 1.8-fold (kidney). Enzyme activities were either decreased or not affected in testes of treated mice and rats. Substituted trifluoroketones ("transition-state" inhibitors of carboxylesterase) were found to be very potent inhibitors of clofibrate-metabolizing carboxylesterase(s) and to be potentially useful in distinguishing among isozymes. The inhibition data suggested that changes in carboxylesterase activity following clofibrate treatment were both qualitative and quantitative.

Original languageEnglish (US)
Pages (from-to)361-369
Number of pages9
JournalToxicology and Applied Pharmacology
Issue number3
StatePublished - 1987


ASJC Scopus subject areas

  • Pharmacology
  • Toxicology

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