Carcinogenesis
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The aim of these studies was to determine the levels of carcinogenic tobacco specific nitrosamines (TSNA) in Sudanese oral snuff (toombak) as recent retrospective epidemiological studies suggested an association between the use of toombak and subsequent development of oral cancer. We have analyzed the TSNA levels in 20 samples of Sudanese toombak, of four different quality levels, collected from five different vendors. Using GC coupled with thermal energy analysis, four TSNA were quantified in snuff extracts: N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), N'-nitrosoanabasine (NAB) and 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK). ⋯ Previously, the highest levels of NNN and NNK reported in any snuff were 0.154 and 0.014 mg/g dry wt respectively. In comparison, the levels in Sudanese toombak were up to 20 and 560 times higher respectively. As the public health implications of these findings are significant, attempts should be made to reduce exposure to TSNA in oral snuff users in Sudan.
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The effect of phenethyl isothiocyanate (PEITC), a dietary inhibitor of carcinogenesis, on the metabolism of the tobacco specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by cultured rat peripheral lung tissues was investigated. Initially, the metabolism of NNK by the tissues was studied by incubating the lung explants in medium containing 1 and 10 microM [5-3H]NNK for 3, 6, 12, and 24 h. NNK metabolites were analyzed and quantified by HPLC and expressed as nmol/mg DNA. ⋯ In general, the inhibition of NNK metabolism was greater when the explants were pre-treated with PEITC. These results suggest that PEITC is an effective inhibitor of the conversion of NNK to metabolites that elicit DNA damage. Our results are in agreement with previously published data in which PEITC was shown to inhibit NNK metabolism and tumorigenesis in the rat lung.