Hormone-mediated oviductal influence on mouse embryo development

This study presents evidence that estradiol, mediated through oviduct fluid, may adversely affect the development of early embryos. Two-cell mouse embryos were cultured in Whitten-Biggers medium with or without 0.2 to 20 microgram/ml of estradiol or progesterone or in mouse oviduct fluid from donors treated with estradiol or estradiol and progesterone. Embryos cultured in fluid from estrogen-dominated donors were significantly less able to develop to morula (65%) or blastocyst (14%) than were those cultured in either Whitten-Biggers medium (91% and 41%) or progesterone-dominated fluid (87% and 36%). Transfer of cultured morulae and blastocysts to uteri of pseudopregnant recipients resulted in 2/3, 4/6, and 0/7 recipients' becoming pregnant for control, progesterone-dominated, and estrogen-dominated, respectively. When estradiol or progesterone was added directly to the control medium, no inhibitory effects were observed at levels higher than those found physiologically in plasma. Protein concentration and osmolalities for representative samples of oviduct fluid were 5.2 mg/ml and 329 mOsM for estrogen-dominated fluid and 1.6 mg/ml and 339 mOsM for progesterone-dominated fluid.