Smokeless tobacco extracts mutate human cells.
Two commercial brands of smokeless tobacco were extracted with water and these extracts were tested in human cell mutation assays. Using the human cell line TK-6 which expresses no cytochrome P450, the two extracts tested were found to be detectably mutagenic in the range 1-3 mg/ml extractable solids. In AHH-1 cells which constitutively express cytochrome P450IAI, a similar result was found for both brands tested. The two extracts were treated with neutral nitrite solutions to mimic physiologic oral conditions or acidic conditions or acidic conditions with nitrite to mimic physiologic gastric conditions. The mutagenicity of both extracts for both TK-6 and AHH-1 cells was markedly decreased by treatment at neutral pH with sodium nitrite (0.25 mM) and by acidic treatment (2 h, pH 3.0). Treatment of extracts with sodium nitrite at pH 3.0 did not have any effect on the mutagenicity of the untreated extracts for TK-6 cells. The mutagenicity of both the extracts destroyed by acidic treatment however, seemed to be restored to a level equivalent to the mutagenicity of the untreated extracts for the TK-6 cells. The same series of experiments with P450-proficient AHH-1 cells showed uniform reduction of mutagenic activity. Since the two cell lines are equally sensitive to mutation by aqueous tobacco extracts it is concluded that mutagenicity is not cytochrome P450 mediated. It would further appear that the extract mutagen(s) is acid and neutral nitrite labile.
Shirnamé-Moré
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Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge 02139.
D015112:4-Nitroquinoline-1-oxide / Q000633:toxicity; D001564:Benzo(a)pyrene / Q000633:toxicity; D002460:Cell Line; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009152:Mutagenicity Tests; D009153:Mutagens; D010947:Plants, Toxic; D014030:Tobacco, Smokeless / Q000633:toxicity*
D009153:Mutagens; D001564:Benzo(a)pyrene; D015112:4-Nitroquinoline-1-oxide