Mutagenic activity of rhodamine dyes and their impurities as detected by mutation induction in Salmonella and DNA damage in Chinese hamster ovary cells.

Commercial rhodamine dyes 6G and B induce His+ reversion mutations in Salmonella and single-strand breaks in Chinese hamster ovary cells, as detected by alkaline sucrose sedimentation. Aroclor 1254-induced rat liver homogenate (S9) is required for production of genetic activity by these dyes. Rhodamine 6G induces both frameshift and base substitution mutations, whereas rhodamine B induces only frameshift mutations. Rhodamine 6G is genetically more active and more toxic than is rhodamine B in both the bacterial and mammalian assays. Rhodamine 6G and B induce doublings of His+ revertants in Salmonella at the doses of 0.02 and 0.52 mumol/plate and shifts in the molecular weight of Chinese hamster ovary DNA at concentrations of 9 x 10(-5) and 9 x 10(-4) M, respectively. All genetic effects assayed demonstrate dose-related increases. Further testing of the pure dyes in Salmonella revealed that rhodamine B loses most of its mutagenicity with purification, whereas rhodamine 6G does not. Impurities from commercial rhodamine B demonstrate the same extent of mutagenicity as the commercial dye.