Comparative mutagenicity of plant-activated aromatic amines using Salmonella strains with different acetyltransferase activities.

Plant systems can activate aromatic amines into mutagens. In the plant cell/microbe coincubation assay, we earlier demonstrated that 2-aminofluorene and m-phenylenediamine were activated by plant cells into mutagens with reversion at the hisD3052 allele in Salmonella typhimurium strain TA98 as the genetic endpoint. New derivatives have been developed which possess elevated levels of acetyl-CoA:N-hydroxyarylamine O-acetyltransferase which are very sensitive to N-hydroxylated amines [Watanabe et al., 1990: Mutat Res 234:337-348]. The objectives of this research were to examine Salmonella strains with different acetyltransferase activities in the plant cell/microbe coincubation assay with a series of structurally related aromatic amines. The hypothesis tested was whether and to what degree a plant-activated metabolite of these aromatic amines could serve as a substrate for bacterial O-acetyltransferase and induce mutation in Salmonella. Every aromatic amine examined was activated by plant cells with YG1024 (the strain with elevated O-acetyltransferase activity) as the genetic indicator organism. The rank order of the mutagenic responses of YG1024 to the plant-activated aromatic amines was 2-aminofluorene > benzidine > m-phenylenediamine > 4-aminobiphenyl > 2,4-diaminotoluene > 2-naphthylamine. This rank order was expressed by TA98 but to a much lower degree. There was a very slight mutagenic response observed in TA98/1,8-DNP6 (a strain lacking O-acetyltransferase activity) with the plant-activated metabolites of benzidine and 4-aminobiphenyl. We conclude that the plant-activated aromatic amines are substrates for bacterial O-acetyltransferases.