Enhancement of radiation effects by mercury in preimplantation mouse embryos in vitro.

Mercuric chloride (3 microM or 10 microM) increased several effects of ionizing radiation (1 Gy) on preimplantation mouse embryos in vitro. Blastocyst formation, hatching of blastocysts, and the number of cells per embryo were affected by this increase in radiation risk. The formation of micronuclei, however, was not influenced either in experiments using mercury alone or in combination experiments with X-rays. Not only was the sum of the single effects exceeded in some of the combination experiments, but the dose-pairs, which were necessary for obtaining a certain effect, clearly fell to the left of the envelope of additivity. That is, the enhancement of effects cannot be explained merely by the shape of the dose-response curves, but there is an interaction between mercury and ionizing radiation.