P-32-postlabelling analysis of DNA adducts with 1-(phenylazo)-2-naphthol (Sudan I, Solvent Yellow 14) formed in vivo in Fisher 344 rats

We report the analysis of DNA adducts with 1-(phenylazo)-2-naphthol in the liver and urinary bladder of Fisher 344 rats treated orally with this dye. DNA adducts were detected and quantitated using the nuclease P1-enhanced ve rsion of the P-32-postlabelling assay. Two variations of multidirectional c hromatographic systems were used to resolve either bulky and/or smaller (po lar) P-32-labelled adducts by TLC. In the present study, a double oral admi nistration of the dye (500 mg/kg) for one day yielded negative results in ( 32)p-postlabelling assay of liver DNA (24 h after dosing). However, three D NA adducts in the urinary bladder were detected under the same conditions o f treatment. Chromatography experiments indicated that the two principal DN A adducts detected in the urinary bladder of Fisher 344 rats were the same as those detected in DNA modified by 1-(phenylazo)-2-naphthol and its metab olite l-(phenylazo)naphthalene-2,6-diol after their activation with peroxid ase in vitro. The results presented here strongly suggest that peroxidase i tself or in a combination with cytochrome P450 participates in the initiati on phase of 1-(phenylazo)-2-naphthol carcinogenesis in the urinary bladder.