Effects of neonatal exposure to diethylstilbestrol on early mouse embryo development in vivo and in vitro.

Eight-week-old female mice of the NMRI strain that had been treated neonatally with diethylstilbestrol (DES, 5 micrograms/day for five days) or not (controls) were treated with gonadotropins to induce ovulation and then were artificially inseminated. Ova or young embryos were recovered from the oviducts on the morning after insemination and on Days 2, 3, and 4. In other experiments, ova were obtained from inseminated females on the morning after ovulation and cultured in vitro. In DES-treated females, a few zygotes developed to the 4-cell stage, but no more advanced stages were seen. Under in vitro conditions, zygotes from DES-treated females developed into blastocysts and to the implantation stage, but the incidence of these stages was lower than with zygotes from controls. Our results point to an abnormal oviductal function in DES-treated females that is not compatible with early embryo survival, even though an additional zygote factor contributing to degeneration of early cleavage stages cannot be excluded.