Carcinogenic azo dyes. XII. Detection of new metabolites of aminoazo dyes by rat liver.

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Abstract
Metabolism of 3''-methyl-4-(dimethylamino)azobenzene (3''-Me-DAB) and 3''-methyl-4-(methylamino)azobenzene (3''-Me-MAB) by the rat liver was investigated by the use of a tracer technique. 3''-Me-DAB[5''-3H] or 3''-Me-MAB[5''-3H] was incubated with a 9000 g supernatant fraction at 37.degree. in an aerobic condition for 30 min. The metabolites were extracted with benzene-acetone. The residual aqueous solution was applied to an Amberlite XAD-2 column and the metabolites were eluted with methanol. The metabolites in the extract or eluate were determined by the reverse isotope dilution analysis after separation by TLC. The recovery of radioactivity in benzene-acetone extract after incubation of 3''-Me-DAB[5''-3H] was 70.8 .+-. 7.5%. About 99.5% of the radioactivity extracted was identified with the N-demethylated, oxidized at 4'' position and ring methyl group, and azo-reduced metabolites and the substrate; 79.4% or 83.8% of radioactivity recovered in each eluate was identified with 3-aminobenzoic acid and 3-acetaminobenzoic acid. The metabolites oxidized at the ring methyl group were also detected in the in vitro metabolism of 3''-Me-DAB or 3''-Me-MAB.