Interaction between radiation and cadmium or mercury in mouse embryos during organogenesis

The response of mouse embryos to different concentrations of cadmium or mercury with or without low LET radiation was measured in terms of gross morphological anomalies and cellular changes. Single doses of the heavy metals (2 mg/kg body weight) were injected i.p. on day 8 of gestation 30 min before whole-body irradiation. Combined exposures to CdCl2 and X-rays led to a significant reduction in the rate of exencephaly compared with the high frequency after cadmium alone. The hypothesis that metallothionein, a sulphur-rich and metal-binding protein, may be responsible for the antagonism observed could not be confirmed. Mercuric chloride alone induced a low rate of exencephaly and the data on combined treatment suggest additivity with 0.5 and 1.0 Gy X-rays. Regarding cellular criteria, cell death in the eye anlage on day 9 of gestation was significantly suppressed after 0.5 Gy and especially after CdCl2 plus 0.5 Gy compared to cadmium alone. It is assumed that the reduction of cell lethality is correlated with the low occurrence of exencephaly. Concerning the proliferation of neuroblasts, cadmium stimulated the mitotic activity whereas X-rays depressed the proliferation capacity. After the combined treatment a distinct antimitotic effect was established.