Histogenesis and dose dependence of N-methyl-N-nitrosourea-induced carcinoma in a localized area of the hamster trachea.

The effect of the number of weekly intratracheal Instillations of N-methyl-N-nitrosourea (MNU) on induction of tracheal tumors was studied in male noninbred Syrian golden hamsters. The histogenesis of metaplastic and neoplastic lesions was also characterized. Treatment of hamsters once weekly for either 6, 8, 10, 12, or 14 weeks with a 0.5% solution of MNU resulted in the induction of a 0, 6, 11, 26, and 42% incidence of carcinoma, respectively, at 6 months after the first MNU treatment. Of the carcinomas induced, 87% were combined epidermoid and adenocarcinomas, whereas 13% were epidermoid carcinomas. In animals killed 1 week following either 1, 3, 6, 8, 10, 12, or 14 treatments, a continuum of metaplastic and neoplastic changes was observed that correlated well with the cancer incidence exhibited at the termination of the study. Mucous cells were found to be of prime importance in the development of the metaplastic and neoplastic tracheal lesions observed.