Further studies on the effect of radiation during the storage of frozen 8-cell mouse embryos at -196 degrees C.

Frozen 8-cell mouse embryos were treated with radiation doses of 0, 10, 50, 100 or 200 cGy gamma-rays at a dose rate of congruent to 5 cGy/day. After thawing the embryos were scored for normal morphological appearance and for development to morulae and blastocysts after 24 h in culture. Embryos from each treatment were then separately transferred to the uteri of pseudopregnant foster mothers which were killed at Day 14 of pregnancy. There was no effect of radiation on morphological appearance, development to morulae and blastocysts, implantation rate, or on the ratio of live fetuses to the number of transferred embryos. As there appeared to be no detrimental effect of up to 200 cGy on frozen 8-cell mouse embryos and, as this is the equivalent of congruent to 2000 years of background radiation, it is concluded that normal levels of background radiation would not be a hazard to the long-term storage of mammalian embryos.