Mutagenic activity of gastric fluid from chewers of tobacco with lime

Although tobacco chewing is strongly associated with a highrisk of oral and upper alimentary tract cancers, the natureof mutagenic exposure among users has not been clearly defined.In this study, tobacco-specific and mutagenic exposure of chewersof tobacco with lime was evaluated by analysis of gastric fluid(GF). The pH, nitrite and cotinine levels of GF samples fromchewers and non-chewers were determined and the samples weretested for mutagenicity in the Ames Sahnonella/microsome assayusing Salmonella typhimurium strains TA98, TA100 and TA102.Cotinine was not detected in GF from non-chewers while the levelsranged between 0.4–13.64 µg/ml in samples from chewers;however, the mean pH values (3.8 ± 0.4 versus 2.8 ±0.3) and nitrite levels (29.40 ± 1.51 versus 27.39 ±0.83 µM) were similar in both groups. While all GF samplesfrom non-chewers were non-mutagenic, samples from chewers weredirectly mutagenic or upon nitrosatlon to all the three testerstrains and to TA102 strain in the presence of S9. Experimentsusing scavengers of reactive oxygen species (ROS) showed thatmannitol and benzoate abolished the mutagenic response of TA102,indicating that ROS are principally responsible for oxidativedamage. The findings provide specific information regardingthe mutagenic exposure among tobacco chewers and suggest thattobacco chewing may be an important risk factor in the developmentof gastric cancer.