The Indirect Effect of Irradiation on Embryonic Development: III. The Contribution of Ovarian Irradiation, Uterine Irradiation, Oviduct Irradiation, and Zygote Irradiation to Fetal Mortality and Growth Retardation in the Rat

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Abstract
Shielding techniques were utilized to differentiate the results of irradiating the ovary, uterus, zygote, and oviduct in the pregnant rat prior to the time of differentiation. Six-day-pregnant rats administered 150 R exhibited the same embryonic mortality and growth retardation whether or not the ovaries were shielded. Nine groups of experimental rats were irradiated on the first day of gestation. The results indicate that neither uterine nor ovarian irraidation at the 150-R dosage contributes to the resulting fetal mortality, which is obviously due to direct irradiation of the oviduct and the ova contained within it. Although it appears most likely that the primary effect is due to the direct effect of irradiating the ova, these experiments do not rule out pathological effects due to oviduct irradiation. The incidence of malformations in the embryos irradiated on the first day and after 6 days of gestation was very low. No instance of exencephaly was observed. These findings further reinforce the difficulty in applying specific teratological findings from one species to man, since there axe apparently marked differences in teratological sensitivity even in the rodent category. The literature dealing with the indirect effect of irradiation on the mammalian embryo is reviewed.