Effect of graded dietary levels of selenium on tracheal carcinomas induced by 1-methyl-1-nitrosourea.

An investigation was conducted to determine the effect of the dietary level of selenium on the induction of tracheal cancer by 1-methyl-1-nitrosourea (MNU). Male Syrian golden hamsters received intratracheal instilations of a 0.5% MNU solution once weekly for 12 weeks. Two weeks prior to the initiation of carcinogen treatment, animals were placed on a semisynthetic, 30% torula yeast diet to which either no selenium or 1 or 5 mg selenium/kg of diet as sodium selenite was added. Animals were maintained on their respective diets for the duration of the study which was terminated 195 days after the first MNU treatment. No significant differences among groups in the incidence of either benign lesions or carcinomas was observed and the distribution of tumor type was similar irrespective of selenium treatment. The results of this study indicate that selenium exerts no chemopreventive effect against MNU-induced tracheal carcinogenesis.