Sex Difference and Carcinogenic Dosage in the Induction of Neoplasms in Salivary Glands of Rats

At low concentrations of DMBA (½% and 1%) twice as many sarcomas and carcinomas of the salivary glands are induced in male as in female rats. Additional oestrogens reduce neoplasms in males by one half while testosterone doubles them in females. The sex difference disappears at the higher dose levels of the carcinogen (2%). Females are more sensitive than males to the toxic effects of DMBA, though less sensitive to the carcinogenic action. Carcinomas rise to a single peak within 240 days while sarcomas appear as late as 770 days with secondary and tertiary peaks. This difference in pattern of induction may be due to the formation of a fibrous capsule separating persisting DMBA-deposits from the epithelial structures and thus protecting them from carcinogenic risk.