Studies on the multidrug resistance gene expression in the livers of rats associated with different susceptibility of hepatocarcinogenesis.
Inbred carcinogen-resistant DRH rat strain developed from the closed colony Donryu rats on the basis of selective markers such as poor induction of gamma-glutamyltranspeptidase and marked reduced incidences of liver tumors during 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) administration, which took more than 10 years. Previously, we observed that the Donryu rat liver was quite sensitive to both DNA-damaging and cytotoxic effects of 3'-Me-DAB, while the DRH rat liver showed tolerance to 3'-Me-DAB under the same conditions. In the present study, we examined mRNA levels related to the cytotoxic drug resistance mechanism in the livers of DRH and Donryu rats using RT-PCR. Contrary to our expectation, we observed rather similar levels of mRNAs between the two rat strains under the following conditions: i) mdr1 mRNA induction after 3'-Me-DAB administration. ii) MLP-2 mRNA reduction by 3'-Me-DAB administration, iii) MLP-2 mRNA induction after cholestasis and iv) constitutive levels of cMOAT gene expression. On the other hand, the levels of p53 mRNA and p53 protein in the Donryu rat liver were higher than those in DRH rat liver during 3'-Me-DAB administration, suggesting that the former were more sensitive to 3'-Me-DAB than DRH rat under these conditions. In conclusion, we failed to demonstrate the difference in the cytotoxic drug resistance mechanism between DRH and Donryu rats at least under the conditions examined in this study.
Gotoh
S
S
Department of Biochemistry, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
Todaka
N
N
Yan
Y
Y
Fukamachi
Y
Y
Abe
T
T
Higashi
K
K
D000818:Animals; D027321:Anion Transport Proteins; D002352:Carrier Proteins / Q000235:genetics; D002779:Cholestasis / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics*; D015870:Gene Expression; D019450:Genes, MDR; D020022:Genetic Predisposition to Disease; D008099:Liver / Q000378:metabolism; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics*; D008297:Male; D008749:Methyldimethylaminoazobenzene; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
D027321:Anion Transport Proteins; D002352:Carrier Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D008749:Methyldimethylaminoazobenzene