Carcinogenesis by urethan via mother's milk and its enhancement of transplacental carcinogenesis in mice.

Pulmonary tumors were induced in mice that were suckled by mothers that received urethan during lactation. More induced tumors appeared in sucklings when urethan was injected into lactating mothers soon after delivery. When pregnant mice were treated with urethan during gestation and lactation their offspring had a significantly increased incidence of pulmonary tumors, and the number of tumors per mouse was compatible with the sum of tumors in mice who received either prenatal or postnatal treatment. However, when prenatal urethan treatment was coupled with postnatal exposure via mother's milk, off