[Mutagenicity of the urine of rats treated with benzidine dyes (author's transl)]

Today industrial use of benzidine is restricted in many countries. However, little attention is paid to those substances which may decompose themselves in the body and release benzidine or benzidine-like substances. I investigated the mutagenicity of urinary ingredients of rats to which benzidine and three kinds of azo dyes were separately administered through the alimentary tract. The azo dyes were Direct Black EX(EX), Direct Green BK(BK), and Direct Bordeaux BK(BK), all having 4,4'-diazobiphenyl group in each structure. The mutagenicity of the urine extract with ether was tested on Salmonella typhimurium TA 98 and TA 100. Urinary metabolites of benzidine showed stronger mutagenicity than benzidine itself on both TA 98 and TA 100 in the presence of S9 mix. EX itself showed mutagenicity only on TA 98, whereas B and BK were nonmutagens. Nevertheless, the urine extract of each azo dye showed strong mutagenicity of the same pattern as benzidine. As a result it is suggested that benzidine might be released in the intestine of experimental animals after the administration of each azo dye. Mutagenic activity of urine sample is important and full of suggestions from the viewpoint of carcinogenicity of aromatic amines.