The functional importance of the oviduct in neonatally estrogenized mouse females for early embryo survival.

Eight-week-old virgin untreated female mice were induced to ovulate using equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG), and were then caged with males overnight. Females with a vaginal plug on the following morning were killed 24 hours later and 2-cell embryos were flushed from the oviduct. These embryos were transferred to the oviduct of 8-week-old control females, to females of the same age treated with 5 micrograms diethylstilbestrol (DES) sc in olive oil for the first 5 days after birth, or to females treated with 1 microgram estradiol-17 beta for 2 days before and 2 days after transfer (estrogen dominated/ED/females). Two days after transfer, a significantly lower number of embryos were recovered from oviducts of DES females compared to control females and a still lower number from ED females. The recovered embryos were cultured in vitro for 4 days testing trophoblast outgrowth ("implantation stage"). The incidence of embryos reaching this stage after development in DES-exposed oviducts was only half of that for embryos passing control oviducts or ED oviducts. It is concluded that the adult oviductal environment in neonatally DES-treated females significantly decreases early embryo developmental potential. The oviductal factor(s) harmful to the embryo may be related to a persistent and possibly increased level of circulating estrogen level in DES females.