Unilateral ovariectomy on the 3rd day of pregnancy in the rat resulted in arrested embryonic development and decreased implantation in the ipsilateral uterine horn. These degenerative changes were apparent 48 hr, but not 24 hr, after operation. A single subcutaneous injection of either oestrone (1·0 μg) or progesterone (2·0 mg) at 08.00 hours on the 5th day of pregnancy induced implantation and foetal maintenance in the ipsilateral horn. Treatment with progesterone was consistently more effective than oestrogen.
These observations suggest that unilateral ovariectomy induces a hormonal deficiency in the adjacent uterine horn which is incompatible with optimum preimplantation embryonic development.
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