Mutation spectra in Salmonella TA98, TA100 and TA104 of two phenylbenzotriazole mutagens (PBTA-1 and PBTA-2) detected in the Nishitakase River in Kyoto, Japan

Previous studies have identified two potent aromatic amine mutagens in the Nishitakase River, a tributary of the Yodo River, which serves as the main drinking water supply for the Osaka area in Japan. The two potent mutagens are 2-[2-(acetylamino)-4-[bis(2-methoxyethyl)amino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-1) and 2-[2-(acetylamino)-4-[N-(2-cyanoethyl)ethylamino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-2). PBTA-1 and PBTA-2 are presumed to be formed from azo dyes discharged in a reduced form from dye factories to sewage treatment plants where they become chlorinated and are then discharged into the river. PBTA-1 and PBTA-2 account for 21% and 17% of the mutagenic activity of the Nishitakase River, respectively. Here we determined the mutation spectra induced by these two mutagens in TA98, TA100, and TA104 at 30-35, 8-10, and 2 x, respectively, above the background. In TA98, the PBTA compounds produced identical mutation spectra, with 100% of the revertants containing the hotspot 2-base deletion of CG within the (CG), sequence. In TA100, 73% of the revertants were GC --> TA transversions, with most of the remaining being GC --> AT transitions; the spectra produced by the two compounds in TA100 were not significantly different (p = 0.8). In TA104, as in TA100, the majority (83%-87%) of the revertants were GC --> TA transversions, with most of the remaining revertants (11%-13%) being AT --> TA transversions. Thus, 83%-87% of the mutations induced by the PBTA compounds in TA104 were at G/C sites. The mutation spectra produced by the two compounds in TA104 were not significantly different (p > 0.08). PBTA-1 and PBTA-2 are structurally similar and have similar mutagenic potencies and mutation spectra in the respective strains. The mutation spectra produced by the PBTA compounds (100% hotspot deletion in TA98 and primarily GC --> TA transversions in TA100 and TA104) are similar to those produced by other potent aromatic amines, which is the class of compounds from which the PBTA mutagens derive. (C) 1999 Elsevier Science B.V. All rights reserved.