Transplacental effects of diethylnitrosamine in Syrian hamsters as related to different days of administration during pregnancy.

Female Syrian hamsters were given a single sc dose of 45 mg diethylnitrosamine (DEN)/kg body weight on 1 of the 15 days of pregnancy. In the offspring of females treated on 1 of the first 11 days of pregnancy, no respiratory tract tumors were found. The offspring of mothers given DEN on 1 of the last 4 days (12-15) of pregnancy developed respiratory tract neoplasms at a rate of up to 95%. A lower incidence of tumors in other organs seemed independent of the day of DEN treatment.