Participation of cytochrome P450 in mutagenic activation of the carcinogen 3'-hydroxymethyl-N,N-dimethyl-4-aminoazobenzene and its N-demethylated compounds by rat liver.
Mutagenicity of the hepatocarcinogen 3'-hydroxymethyl-N, N-dimethyl-4-aminoazobenzene (3'-CH2OH-DAB) and its N-demethylated compounds was examined. Rat-liver 9000 X g supernatant (S9) fraction was used together with Salmonella typhimurium TA98 or TA100 as a tester strain. The expression of mutagenicity of 3'-CH2OH-DAB, 3'-hydroxymethyl-N-methyl-4-aminoazobenzene (3'-CH2OH-MAB) and 3'-hydroxymethyl-4-aminoazobenzene (3'-CH2OH-AB) required the presence of both microsomes and cytosol as sources of enzymes as well as NADPH as a cofactor. 3'-CH2OH-AB showed positive mutagenicity on both strains in the presence of liver S9 from untreated rats whereas 3'-CH2OH-DAB and 3'-CH2OH-MAB were negative. The treatment of rats with polychlorinated biphenyls (PCB) or 3-methylcholanthrene (3-MC) resulted in a marked increase in the ability of S9 to activate these three compounds, whereas phenobarbital (PB) induction was not effective, except for the activation of 3'-CH2OH-AB. The mutagenic activities of the three compounds in strain TA98 were considerably decreased by adding cytochrome c to the S9 mixture, but the activation reactions were insensitive to 1-(1-naphthyl)-2-thiourea (NTU) and methimazole, high-affinity flavin-containing monooxygenase (FMO) substrates. Metyrapone and 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF-525A, potent inhibitors of cytochrome P450, had no inhibitory effect on the activation of these compounds by S9 from PCB-treated rat livers. In contrast, 7,8-benzoflavone (BF), a specific inhibitor of cytochrome P448, decreased the activities of 3'-CH2OH-DAB and 3'-CH2OH-MAB by 88 and 78%, respectively, but the inhibition was negligible for 3'-CH2OH-AB.
D000818:Animals; D001711:Biotransformation; D002273:Carcinogens / Q000378:metabolism*; D003043:Cocarcinogenesis; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008749:Methyldimethylaminoazobenzene / Q000031:analogs & derivatives* / Q000378:metabolism; D009152:Mutagenicity Tests; D051381:Rats; D011919:Rats, Inbred Strains; D012486:Salmonella typhimurium / Q000187:drug effects; D004124:p-Dimethylaminoazobenzene / Q000031:analogs & derivatives*
D002273:Carcinogens; C032237:3'-hydroxymethyl-4-(dimethylamino)azobenzene; D008749:Methyldimethylaminoazobenzene; D003577:Cytochrome P-450 Enzyme System; D004124:p-Dimethylaminoazobenzene