STABLE EXPRESSION OF HUMAN CYP2E1 IN CHINESE-HAMSTER CELLS - HIGH-SENSITIVITY TO N,N-DIMETHYLNITROSAMINE IN CYTOTOXICITY TESTING

Involvement of human CYP2E1 expressed in genetically engineered cells in the metabolic activation of promutagens and procarcinogens was stud ied, An expression plasmid containing an insert of CYP2E1 cDNA and SR alpha promoter was constructed and transfected into the cultured cell line CR-119 which had previously been established by introducing a cDN A coding for NADPH-cytochrome P450 reductase. Among newly established cell lines, ER-181 showed the highest expression of CYP2E1 mRNA. Produ ction of the CYP2E1 protein was confirmed by Western blot analysis usi ng anti-rat CYP2E1 antibodies. Assay of 7-ethoxycoumarin O-deethylase activity demonstrated that ER-181 cells acquired the catalytic functio n of CYP2E1. ER-181 cells showed higher sensitivity to N,N-dimethylnit orosamine (DMN) in cytotoxicity assays as compared to parental CR-119 cells. Hypersensitivity to DMN of ER-181 cells was completely suppress ed by 3-amino-1,2,4-triazole, a known inhibitor of CYP2E1. These resul ts indicate that ER-181 cells which express human CYP2E1 are a useful tool to investigate toxicological functions of the cytochrome.