The effects of the progesterone antagonist RU-486 on mouse preimplantation development in vitro and in vivo.
We have evaluated the effects of RU-486 on preimplantation development in the mouse. Female mice received a subcutaneous injection of 1mg RU-486 with hCG on the morning post-coitus. Two-cell embryos were recovered from the oviducts and cultured in the presence or absence of RU-486. Three days later we found that 2-cell embryos exposed to RU-486 in vivo developed to the blastocyst stage at rates similar to control regardless of whether RU-486 was present in culture medium. Transfer experiments revealed that embryos retrieved from RU-486-treated females developed normally in the reproductive tracts of non-treated control foster mothers. However, when control 2-cell embryos were transferred to RU-486-treated foster mothers, development was not supported. We conclude that the contragestational properties of periovulatory treatment with RU-486 is not the result of a direct effect on the cleavage stage embryo but on the reproductive tract of the mother.