Studies on Carcinogenic Azo Dyes. II. Metabolism of 3'-Methyl-4-dimethyl-aminoazobenzene with the Rat Liver by the Use of Tracer Technique

Abstract

3'-Methyl-4-dimethylamino azobenzene[5'-³H](3'-Me-DAB) was incubated with rat liver slices for 3 hours or with liver homogenates for 2 hours, and 85.0±3.8% (slice sample) or 73.0±3.7% (homogenate sample) of the radioactivity added was recovered in the benzene-acetone (1 : 1) layer from the incubation mixture. The metabolites in the extracts were separated by thin-layer chromatography and identified by the reverse isotope dilution analysis. More than 95% of the radioactivity of the benzene-acetone layer was identified with the unchanged substrate and the metabolites such as N-demethylated, 4'-hydroxylated, and azo-reduced products. By measuring ³H-activity of the azoreduced metabolites from 3'-Me-DAB[5'-³H], the azo reductase activity may be assayed more directly than by colorimetric methods, 3'-Methyl-4-methylamino azobenzene [5'-³H] was also incubated with rat liver for studying its conversion to 3'-Me-DAB. As the result, it was found that N-methylation did not occur in the metabolism of the aminoazo dyes by liver slice of a rat.