- Email: [email protected]
An improved method for detecting mutagens
285 (10-6--10 -4 M) increase SCEs. Thus, some chemicals that are positive in the Salmonella test are negative in the mammalian SCE system. It is not yet known if this is a reflection of a difference in the sensitivities of the t w o tests, or of the ability of the SCE test to discriminate between those chemicals that are active in bacteria but not in mammals.
223 Yahagi, T., M. Nagao, T. Matsushima, Y. Seino, N. Sawamura, A. Shirai, T. Kawachi and T. Sugimura, National Cancer Center Research Institute, T o k y o and Institute of Medical Sciences, University of T o k y o , T o k y o (Japan)
An improved method for detecting mutagens The assay m e t h o d was improved in order to obtain a better correlation between mutagens and carcinogens. First, we modified the Ames standard plate method by a prior incubation step, the liquid method. In this system, the indicator bacteria and test substance were preincubated with S-9 Mix for 20-30 min at 30 or 37 ° and then poured onto a plate for the growth of the mutants. By this new method, which is as simple as Ames standard assay, we could detect the mutagenicity of many N-nitrosamines, including dimethylnitrosamine, which could not be detected heretofore without preincubation. Second, we improved the composition of S-9 Mix by including NADH and ATP in addition to NADPH. Using this new S-9 Mix, 4-dimethylaminoazobenzene, which was a weak mutagen without NADH and ATP, induced more revertants. Third, in the case of complex azo-dyes, riboflavin was further added to the S-9 Mix. Thus, a carcinogenic azo-dye, such as Ponceau R, was found to be mutagenic only with riboflavin. Mutagenicities of other azo-dyes including Congo Red, Benzopurpurine 4B, Chlorazol Violet N, and Eriochrom Blue Black BH were similarly detected. With this method, we investigated the mutagenicity of more than 600 chemicals, including carcinogenic and non-carcinogenic materials and substances with u n k n o w n carcinogenicity utilizing the Ames tester strains Salmonella typhimurium TA100 and TA98. We obtained a high correlation between mutagens and carcinogens. Thus, 86% of 158 carcinogens were mutagenic, and 74% of 81 non-carcinogens were non-mutagenic. With the unknowns, 178 c o m p o u n d s were mutagenic. The conditions to demonstrate the mutagenicity of some type of carcinogens such as a-benzenehexachloride, 1,1-and 1,2-dimethylhydrazine, 3-hydroxyanthranilic acid, safrole and urethane are being investigated.
224 Zetterberg, G., Department of Genetics and Plant Breeding, University of Uppsala, S-750 07, Uppsala (Sweden) Mutagenicity o f chlorinated phenoxyacetic acids in Saccbaromyces cerevisiae
223 Yahagi, T., M. Nagao, T. Matsushima, Y. Seino, N. Sawamura, A. Shirai, T. Kawachi and T. Sugimura, National Cancer Center Research Institute, T o k y o and Institute of Medical Sciences, University of T o k y o , T o k y o (Japan)
An improved method for detecting mutagens The assay m e t h o d was improved in order to obtain a better correlation between mutagens and carcinogens. First, we modified the Ames standard plate method by a prior incubation step, the liquid method. In this system, the indicator bacteria and test substance were preincubated with S-9 Mix for 20-30 min at 30 or 37 ° and then poured onto a plate for the growth of the mutants. By this new method, which is as simple as Ames standard assay, we could detect the mutagenicity of many N-nitrosamines, including dimethylnitrosamine, which could not be detected heretofore without preincubation. Second, we improved the composition of S-9 Mix by including NADH and ATP in addition to NADPH. Using this new S-9 Mix, 4-dimethylaminoazobenzene, which was a weak mutagen without NADH and ATP, induced more revertants. Third, in the case of complex azo-dyes, riboflavin was further added to the S-9 Mix. Thus, a carcinogenic azo-dye, such as Ponceau R, was found to be mutagenic only with riboflavin. Mutagenicities of other azo-dyes including Congo Red, Benzopurpurine 4B, Chlorazol Violet N, and Eriochrom Blue Black BH were similarly detected. With this method, we investigated the mutagenicity of more than 600 chemicals, including carcinogenic and non-carcinogenic materials and substances with u n k n o w n carcinogenicity utilizing the Ames tester strains Salmonella typhimurium TA100 and TA98. We obtained a high correlation between mutagens and carcinogens. Thus, 86% of 158 carcinogens were mutagenic, and 74% of 81 non-carcinogens were non-mutagenic. With the unknowns, 178 c o m p o u n d s were mutagenic. The conditions to demonstrate the mutagenicity of some type of carcinogens such as a-benzenehexachloride, 1,1-and 1,2-dimethylhydrazine, 3-hydroxyanthranilic acid, safrole and urethane are being investigated.
224 Zetterberg, G., Department of Genetics and Plant Breeding, University of Uppsala, S-750 07, Uppsala (Sweden) Mutagenicity o f chlorinated phenoxyacetic acids in Saccbaromyces cerevisiae