Developmental malformations and intrauterine deaths in gamma-ray-irradiated scid mouse embryos

Purpose: To examine the induction by radiation of developmental malformations and intrauterine deaths in severe combined immunodeficiency (scid) mice. Materials and methods: The scid embryos, as well as those of C.B-17 control mice, were irradiated with graded doses of 60Co gamma-rays on gestation day 8. Results: Intrauterine deaths in scid mice increased with radiaton dose, and their frequency was substantially higher than in C.B-17 mice. The LD50 for intrauterine death in scid mice was 0.58 Gy and 1.25 Gy in C.B-17 mice. In addition, after irradiation scid mice showed several types of developmental malformations, including meningoencephalocele, spina bifida, eye defects, tail defects and oedema. Malformation incidences were higher in scid than in C.B-17 mice: 33.3% in scid mice irradiated with 0.75 Gy and 13.0% in C.B-17 mice irradiated with 1.0 Gy. However, when malformation incidences were plotted against intrauterine deaths, all the data, irrespective of the type of mouse, essentially fell along a single straight line. Conclusions: These results suggest that some mechanism common to both scid and normal mice induces developmental malformations. This mechanism involves cell killing. Residual DNA damage, such as double-strand breaks, could be associated with radiation-induced teratogenesis.