Radiation damage in mouse embryos exposed to 1 rad x-rays or negative pions.

Pregnant mice of two different strains (F/A and NMRI) were exposed to 1 rad of whole-body pion- or X-irradiation at day 8 of gestation. Lucanthone (Miracil D), a known radiosensitizer in various biological systems, was applicated 30 min before irradiation. Five days after treatment the fetuses were observed for developmental anomalies. In both strains of mice it was found that the radiation dose as low as 1 rad results in a significant increase in the rate of abnormal fetuses compared to nonirradiated, but restrained fetuses. Comparing the effectiveness of negative pions (peak irradiation) with X-rays for teratogenic effects, the RBE was between 1.7 and 1.9. The application of Lucanthone increased the number of damaged fetuses and led to various degrees of sensitization depending on the mouse strain and dosage used. Differences between the strains as regards the frequency of damages are explained by different development stages at the time of treatment.