Bacterial mutagenicity of some tobacco aromatic nitrogen bases and their mixtures

The first aim was to compare the genotoxicities of two tobacco-specific nitrosamines (TSNA), 4-(methylnitrosamino)-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) in two types of tests, the Salmonella reverse mutation assay (250-2000 microg per plate) and the Mutatox test (up to 1000 microg/ml) using dark mutant M-169 of Vibrio fischeri. The second aim was to assess the effects of single other tobacco chemicals and metabolites (nicotine (NIC), cotinine (COT), trans-3-hydroxycotinine (3HC), cotinine-N-oxide (CNO) and nicotine-N-oxide (NNO)) on the mutagenic responses at relative concentrations observed physiologically. The Salmonella strains were TA100, TA7004, TA7005, and TA7006, all showing missense backmutations that are characteristic of the TSNA. NNN was a direct mutagen to strains TA100, TA7004, and in the Mutatox test, and was not mutagenic in the presence of rat or hamster S9. NNK was mutagenic only in strain TA7004 with rat and hamster S9, but not in TA100, but was directly mutagenic in the Mutatox test. While all the other tobacco chemicals were not mutagenic alone to strains TA100 and TA7004 in the presence and absence of rat or hamster S9, the Mutatox test produced direct mutagenicity for COT, 3HC, and NNO, but not CNO. The latter was mutagenic in the Mutatox test with rat or hamster S9, but only rat S9 was effective for COT, NNO and 3HC. Inhibitory potentiations of NNN by NIC and COT were observed on strain TA7004, and by NIC on strain TA100. There were no interactions on NNK in the presence of S9 for strain TA7004 or TA100. In contrast, a complex inhibition and enhancement behavior occurred in the Mutatox test for each interaction, but no effects were observed for CNO on NNK without S9, and few for NIC on NNK with hamster S9. Compounds which showed no activity alone modulated the genotoxicity of two potent TSNAs in both types of tests.