Transplacental induction of gonadal tumors in rats by a nitrosamine

Ovarian and testicular tumors were induced in the offspring (F1 generation) of MRC rats that received single or multiple doses of N-nitrosobis(2-oxopropyl)amine on the 14th, 18th, and/or 20th days of pregnancy. The ovarian tumor incidence was significantly higher (46%) in the F1 generation exposed to the carcinogen a single time at the 18th day of gestation, when compared to those exposed at the 14th (P less than 0.005) or 20th days (P less than 0.025), and was highest in those exposed to N-nitrosobis(2-oxopropyl)amine repeatedly (at the 14th through 20th days of gestation). Morphologically ovarian tumors were of a mixed stromal cell-coelomic type. Testicular tumors were of mixed Leydig cell-glandular types and occurred in a higher incidence in the F1 generation exposed to N-nitrosobis(2-oxopropyl)amine at the 14th through 20th day of gestation, compared with those exposed to the carcinogen at other times of the gestation period (P less than 0.0005). This is the first report of transplacental gonadal tumor induction by a nitrosamine.