Induction of rat liver microsomal and nuclear cytochrome P-450 by dietary 2-acetylaminofluorene and butylated hydroxytoluene.
The influence of dietary 2-acetylaminofluorene (AAF) on the cytochrome P-450 content of rat liver microsomal and nuclear fractions was immunochemically probed with monoclonal and polyclonal antibodies to cytochromes P-450c and P-450d. Cytochrome P-450d but not P-450c was immunodetected in microsomes, nuclear envelopes, and nuclei from untreated rats. The levels of both cytochromes P-450c and P-450d were elevated after a diet of either 0.1% AAF for 1 week or 0.05% AAF for 3 weeks. However, the level of cytochrome P-450c relative to P-450d was lower after the more prolonged AAF feeding. Supplementation of AAF-containing diets with 0.3% butylated hydroxytoluene (BHT), which affords protection against AAF hepatocarcinogenesis in high-fat fed rats, protected and/or induced total (spectral) nuclear envelope cytochrome P-450 content. Immunochemical studies of liver fractions showed that BHT enhanced the AAF-dependent induction of cytochrome P-450c, but not of P-450d. This was a concerted effect of AAF + BHT since dietary BHT by itself did not affect the levels of cytochrome P-450c or P-450d as compared to control rats. Since 1- to 3-week dietary AAF had little effect on total (spectral analyses) microsomal cytochrome P-450 but markedly reduced total P-450 in nuclear envelopes, the coordinated induction of specific cytochrome P-450s in the different fractions suggests selective induction and depression of different forms of cytochrome P-450 and provides additional evidence for independent regulation of the drug-metabolizing system in nuclear envelope and microsomes. In addition, these results suggest that regulation of cytochrome P-450 may play a crucial role in the nutritional modulation of AAF hepatocarcinogenesis.
Laboratory of Molecular Carcinogenesis, National Cancer Institute, Bethesda, MD 20892.
F K
FK
Friedman
H
H
Miller
S S
SS
Park
S A
SA
Graham
H V
HV
Gelboin
R
R
Carubelli
D015073:2-Acetylaminofluorene / Q000494:pharmacology*; D000818:Animals; D000911:Antibodies, Monoclonal; D002084:Butylated Hydroxytoluene / Q000494:pharmacology*; D002467:Cell Nucleus / Q000201:enzymology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000276:immunology; D004032:Diet; D004790:Enzyme Induction / Q000187:drug effects; D015151:Immunoblotting; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains
D000911:Antibodies, Monoclonal; D002084:Butylated Hydroxytoluene; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D015073:2-Acetylaminofluorene