Cytochrome P450 2B enzyme (CYP2B) induction defect following phenobarbital treatment in the fa/fa Zucker rat: molecular characterization

R A Blouin; A M Bandyopadhyay; I Chaudhary; L W Robertson; B Gemzik; A Parkinson

doi:10.1006/abbi.1993.1289

Back

Cytochrome P450 2B enzyme (CYP2B) induction defect following phenobarbital treatment in the fa/fa Zucker rat: molecular characterization

Journal article

Peer reviewed

Cytochrome P450 2B enzyme (CYP2B) induction defect following phenobarbital treatment in the fa/fa Zucker rat: molecular characterization

R A Blouin, A M Bandyopadhyay, I Chaudhary, L W Robertson, B Gemzik and A Parkinson

Archives of biochemistry and biophysics, Vol.303(2), pp.313-320

06/1993

DOI: 10.1006/abbi.1993.1289

PMID: 8512318

View Online

Abstract

The present study describes the mechanism of the dampened induction of the CYP2B1 and CYP2B2 genes following phenobarbital treatment in the phenotypically obese fa/fa Zucker rat. The fa/fa Zucker rat demonstrated a threefold lower level of CYP2B1/2B2 enzyme induction, as indicated by reduced testosterone oxidation at the 16 beta position and resorufin formation from pentoxy- and benzyloxyresorufin, protein concentration (Western blot analysis), and steady-state mRNA levels (Northern and slot blot analyses) following in vivo treatment with phenobarbital than the Fa/? littermate controls. A primary hepatocyte cell culture system was used to determine if the dampened induction of the CYP2B1/2B2 enzyme is dependent on hormonal influences. Phenobarbital-treated (0.75 mM) hepatocytes from fa/fa Zucker rats showed approximately a three-fold lower induction response based on measurements of CYP2B1/2B2 (R-17 cDNA probe) and CYP2B1 (oligo probe) mRNAs. In order to evaluate whether this dampened response was at the level of transcriptional activation or initiation, as opposed to altered message stability, we measured the rate of transcription of CYP2B1/2B2 genes in nuclei from cultured hepatocytes during run-off experiments. Compared to Fa/? controls, the fa/fa Zucker rat had a greater than threefold lower nuclear transcription rate of CYP2B1/2B2 mRNA. These results suggest that the defective induction of the CYP2B1 and CYP2B2 genes exists at the transcriptional level in the mutant obese fa/fa Zucker rat. These data provide strong evidence that at least two genes are involved. Multiple gene involvement would suggest that the defect is not due to a mutation of the CYP2B gene cis-acting sequence. Instead, the lack of binding of a trans-acting factor, the presence of a repressor, or a defect in transcriptional activation is more likely the molecular mechanism(s) for this enzyme induction defect.

Mutation

Phenobarbital - pharmacology

DNA Probes

Transcription, Genetic - drug effects

Liver - enzymology

Oxidation-Reduction

Oxidoreductases - genetics

Cells, Cultured

Rats

Male

RNA, Messenger - metabolism

Blotting, Western

Rats, Zucker

Testosterone - metabolism

Blotting, Northern

Oxazines - metabolism

Animals

Liver - drug effects

Cytochrome P-450 Enzyme System - genetics

Obesity - enzymology

Cytochrome P-450 CYP2B1

Details

Title: Subtitle: Cytochrome P450 2B enzyme (CYP2B) induction defect following phenobarbital treatment in the fa/fa Zucker rat: molecular characterization
Creators: R A Blouin - Division of Pharmacology and Experimental Therapeutics, College of Pharmacy, University of Kentucky, Lexington 40536-0082
A M Bandyopadhyay
I Chaudhary
L W Robertson
B Gemzik
A Parkinson
Resource Type: Journal article
Publication Details: Archives of biochemistry and biophysics, Vol.303(2), pp.313-320
Publisher: United States
DOI: 10.1006/abbi.1993.1289
PMID: 8512318
ISSN: 0003-9861
eISSN: 1096-0384
Grant note: GM 42058 / NIGMS NIH HHS ES 03765 / NIEHS NIH HHS
Language: English
Date published: 06/1993
Academic Unit: Occupational and Environmental Health
Record Identifier: 9984002498302771

Metrics

22 Record Views

36 Times Cited - Web of Science