THE EFFECT ON IMPLANTATION OF TREATING CULTURED MOUSE BLASTOCYSTS WITH OESTROGEN IN VITRO AND THE UPTAKE OF [3H]OESTRADIOL BY BLASTOCYSTS

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Abstract
SUMMARY: The present experiments were undertaken in an attempt to determine whether oestrogen can directly affect implantation in the mouse embryo. To test this, mouse ova were cultured from the two-cell stage to blastocysts and transferred to ovariectomized foster mothers treated with progesterone from the time of ovariectomy. The implantation response was scored 4 days after transfer. Doses of 0·2, 0·4 and 0·8 mg. progesterone/day were tested and the effect of exogenous oestrogen at each dose level determined. The threshold dose of progesterone appears to be between 0·4 and 0·8 mg./day. Above threshold, significantly more foster mothers had implantation sites when oestrogen was injected than when it was not. Mouse blastocysts cultured in vitro were treated with varying concentrations of oestradiol, washed, and then transferred to foster mothers receiving only progesterone. The implantation response was significantly higher when blastocysts treated with 10−8 m-oestradiol were transferred to foster mothers than when untreated control blastocysts were transferred. This finding implies that there is a direct relationship between the action of oestradiol on the blastocyst and implantation. Additional information was obtained to show that [3H]oestradiol was taken up and bound by blastocysts cultured in vitro.