Comparison of the levels of enzymes involved in drug metabolism between transgenic or gene-knockout and the parental mice.
Drug-metabolizing enzymes are involved in the metabolic activation or detoxification of carcinogens. To evaluate animals developed as models for alternative carcinogenicity testing, we investigated whether or not a gene manipulation including the transgene of ras and the knocking out of a tumor suppressor gene such as p53 or XPA could alter the expression of representative drug-metabolizing enzymes directly or indirectly. Expression of several isoforms of cytochrome P450 (CYP) in the liver of rasH2, p53 (+/-), Tg.AC, and XPA (-/-) mice with or without treatment of prototype inducer. phenobarbital or 3-methylcholanthrene, was analyzed by Western immunoblotting in comparison with their parental strains of mice. In addition, the activities of 3 major phase II enzymes, UDP-glucronosyltransferase, sulfotransferase, and glutathione S-transferase, were compared between the gene-manipulated and the corresponding parental strains of mice. Results demonstrate that XPA gene knockout appeared to increase constitutive expression of CYP2B and CYP3A isoforms. Overexpression of human c-Ha-ras gene or p53 gene knockout appeared to increase constitutive UGT activity toward 4-nitrophenol. The content or activities of almost all other enzymes examined in the present study do not appear to be affected by the gene manipulation.
Ariyoshi
N
N
Laboratory of Drug Metabolism, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Imaoka
S
S
Nakayama
K
K
Takahashi
Y
Y
Fujita
K
K
Funae
Y
Y
Kamataki
T
T
D000826:Animal Testing Alternatives; D000818:Animals; D015197:Carcinogenicity Tests / Q000379:methods*; D002273:Carcinogens / Q000633:toxicity; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D004195:Disease Models, Animal; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D016158:Genes, p53; D011905:Genes, ras; D007527:Isoenzymes; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D016601:RNA-Binding Proteins / Q000235:genetics; D051381:Rats; D051760:Xeroderma Pigmentosum Group A Protein
D002273:Carcinogens; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D016601:RNA-Binding Proteins; D051760:Xeroderma Pigmentosum Group A Protein; C497315:Xpa protein, mouse; D003577:Cytochrome P-450 Enzyme System