Carcinogenic azo dyes. XI. Analysis of biliary and urinary metabolites of 3'-methyl-4-(methylamino)azobenzene in rat.

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Abstract
Metabolites of 3''-methyl-4-(methylamino)azobenzene (3''-Me-MAB) in the rat bile and urine were investigated by use of a tracer technique. 3H-3''-Me-MAB in cottonseed oil was administered orally by a stomach tube. The dye metabolites in the bile and urine collected during 24 h after the administration were hydrolyzed with .beta.-glucuronidase/arylsulfatase. The hydrolyzed metabolites were then extracted with chloroform or separated by chromatography on an Amberlite XAD-2 using methanol as solvent. The metabolites in the chloroform extract or methanol eluate were identified by the reverse isotope dilution analysis, after or before separation by TLC. The N-demethylated, aryl hydroxylate, and their azo-reduced products were detected in the bile, in addition to the products oxidized at the ring methyl group as the new metabolites of 3''-Me-MAB. The metabolites retaining the azo-linkage were hardly excreted in urine. Instead, 3-aminobenzoic acid, 3-amino-6-hydroxytoluene and their N-acetylated products were major metabolites in urine. The metabolism for 3''-Me-MAB in the rat probably involves oxidation at the ring methyl group. Effect of the ring methyl group on the carcinogenic action of aminoazo dyes is discussed.