Transplacental Induction of Gonadal Tumors in Rats by a Nitrosamine1

Ovarian and testicular tumors were induced in the offspring (Fi gen eration) of MRC rats that received single or multiple doses of Nnitrosobis(2-oxopropyl)amine on the 14th, 18th, and/or 20th days of pregnancy. The ovarian tumor incidence was significantly higher (46%) in the FI generation exposed to the carcinogen a single time at the 18th day of gestation, when compared to those exposed at the 14th (P < 0.005) or 20th days (P < 0.025). and was highest in those exposed to yV-nitrosobis(2-oxopropyl)amine repeatedly (at the 14th through 20th days of gestation). Morphologically ovarian tumors were of a mixed stremai cell-coelomic type. Testicular tumors were of mixed Leydig cell-glandular types and occurred in a higher incidence in the F, generation exposed to A'-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 < 0.0005). This is the first report of transplacental gonadal tumor induction by a nitros-