Tissue differentiation as a prerequisite for transplacental carcinogenesis in the hamster respiratory system, with specific respect to the trachea.

The significance of tissue differentiation for the transplacental carcinogenicity of DEN was examined. In one experiment, pregnant Syrian golden hamsters received a single sc injection of DEN on one of the different days of pregnancy. Approximately 95% of the offspring of those mothers treated on one of the last 4 days (days 12--15) of gestation developed respiratory tract tumors. Transplacental DEN treatment before the 12th prenatal day failed to induce any neoplastic response in the young. In the second experiment, the differentiation of the prenatal Syrian golden hamster tracheal epithelium was examined histologically and by electron microscopy. We found that on the 12th prenatal day the ER occurred for the first time in its functionally competent form. On earlier prenatal days, the epithelial cells lacked this organelle. We conclude that this development of ER is a prerequisite for transplacental DEN carcinogenesis, since this organelle contains the nonspecific enzyme systems necessary for the transformation of DEN to its ultimate carcinogen.