In the present study, SOS-inducing activity of 76 basic dyes was investigated by umu test using Salmonella typhimurium TA1535/pSK1002 under the condition of absence and presence of rat liver microsomal fraction. The test was carrid out with five doses of basic dyes (400, 120, 40, 12, and 4 μg/ml). The samples showing β-galactosidase activity more than 1.5-fold over the background level were reexamined and the dose-response curves were prepared at various doses. Thereafter, samples showing β-galactosidase activity unit more than 1.5-fold of the background level were defined as genotoxic. Among the basic dyes examined, 13 compounds induced umu gene expression. The potent genotoxic compounds without metabolic activation were Blue 40, Blue 47, Brown 14, Orange 30, Red 24, Violet 30, Violet 31, Yellow 13 (h), Yellow 19, Yellow 25, Yellow 67, and Yellow 73 and in the presence of S9, Orange 47 was judged as genotoxic in addition to the aforementioned dyes. An evident dose-response relationship between the doses of the dye and umu gene expression was observed in these 13 dyes.
