Embryo mortality and altered uterine luminal proteins in progesterone-treated rabbits.

ABSTRACT

PIP: Embryo mortality and altered uterine luminal proteins were studied in progesterone-treated rabbits. Progesterone was injected into rabbits on Days -2, -1, and 0 (the day of mating) at doses of .5, 1, and 1 mg, respectively. Normal fertilization rates resulted, however, embryonic death occurred by Day 4. Embryos in progesterone-treated does for up to 3 days survived normally when transferred to normal recipients, whereas Day 4 embryos from treated does exhibited a reduced ability to implant. The uterine fluid (UF) protein pattern was examined on Days 1-7 after mating. Total UF protein levels were significantly greater (p less than .05) in treated animals on Day 4 than in controls. Uteroglobin secretion was significantly advanced (p less than .05) in the treated animals by Day 3. Examination revealed a delay in the time of the arrival of embryos into the uterus in progesterone-treated rabbits. This delay, coupled with the earlier secretion of uteroglobin in the treated- rabbits, suggested a possible asynchrony of approximately 1 day between embryo arrival in the uterus and certain uterine proteins. Embryonic development in vitro and in vivo was examined after exposure to UF collected at various gestational stages. More normal Day 3 morulae placed in UF from Day 3 control and Day 2 progesterone-treated rabbits developed than similar morulae placed in UF from Day 2 controls and Day 3 progesterone-treaded does. Therefore, partial physiologic synchrony was achieved, suggesting that ''asynchronous'' UF can be embryotoxic. It is concluded that the ability of does to produce young at a pregnancy immediately following a progesterone-treated pregnancy was not impaired.