A solvent effect on the mutagenicity of tryptophan-pyrolysate mutagens in the Salmonella/mammalian microsome assay

The effect of adding organic solvents to the pre-incubation mixture in the Salmonella/mammalian microsome assay was examined in tests of the tryptophanpyrolysate mutagens, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). Acetonitrile enhanced the mutagenic activity of Trp-P-1 and Trp-P-2 by an order of magnitude under optimal conditions. Strong enhancement of mutagenicity was also observed for the addition of ethanol, methanol, tetrahydrofurfuryl alcohol, tetrahydrofuran, 1,2-dimethoxyethane and N,N-dimethylformamide. The enhancing effect of acetonitrile on the mutagenicity of Trp-P-2 was found to be result of enrichment of the active metabolite in the assay system.