Abstract
Some chemical carcinogens, such as urethane and diethylnitrosamine, have been shown to produce carcinogenic effects on the fetus in utero (1, 2). In the case of the polycyclic hydrocarbon carcinogens, the data are quite unclear. A number of investigations have demonstrated that administration of polycyclic hydrocarbon carcinogens to pregnant animals will result in an increased number of tumors in their progeny (3–7). However, in these experiments, the offspring have been allowed to nurse on their own mothers. Since polycyclic hydrocarbon carcinogens will appear in the milk, a distinction cannot be made between prenatal and postnatal exposures (8). The studies to be presented were designed to distinguish between these two possibilities. The progeny of female mice which had received subcutaneous injections of benzo(a)pyrene (BP) during the latter half of pregnancy were delivered by caesarean section and nursed on foster mothers from a control group which had not received injections of any type. Thus, any carcinogenic effect which resulted from administration of the carcinogen would have occurred during the prenatal period. In the experiments to be reported the presence and number of pulmonary adenomas have been determined. The mouse lung is highly sensitive to chemical carcinogens, and such exposures result in formation of pulmonary adenomas (9). A second tissue which has received special attention is the skin. Weak carcinogenic effects in the skin, such as initiation, can be elicited or accelerated by subsequent topical application of croton oil (10) and this procedure has been employed. In addition to the study of these two sensitive indices of a carcinogenic effect, the presence of tumors in other tissues was also searched for at autopsy.
Materials and Methods. Female Ha/ICR mice obtained from Millerton Farms, N.Y. were used for the study of carcinogenesis.
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