Ultimate forms of mutagenic and carcinogenic heterocyclic amines produced by pyrolysis

A mutant strain of Salmonella typhimurium TA98/1,8-DNP6 isolated by McCoy et al. (1) was reported to be defective in esterifying activity. We have found that 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1), 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2), 2-amino-3-methylimidazo-[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) were not mutagenic to TA98/1,8-DNP6 with S9 mix, while these compounds were strongly mutagenic to the original TA98 with S9 mix. The mutagenicities of some of these heterocyclic amines to TA98 were inhibited by pentachlorophenol, an aryl sulfotransferase inhibitor. These results indicate that the ultimate forms of these heterocyclic amines are probably sulfate esters of heterocyclic amine N-hydroxides. Contrary to this, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), 2-amino-9H-pyrido[2,3-b]indole (A alpha C) and 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeA alpha C) were definitely mutagenic to TA98/1,8-DNP6, although less than to TA98.