Abstract
Summary
Immature rats of 22 or 30 days of age pretreated with an ovulatory dose of pregnant mare serum (PMS) were used. Statistically significant compensatory ovulation was found in rats treated with 4 IU PMS on Day 30 followed by unilateral ovariectomy on Day 31. No compensatory ovulation followed unilateral ovariectomy in rats treated with 25 IU PMS on Day 22 or Day 30. In rats treated with 3 IU PMS on Day 22 and unilaterally ovariectomized on Day 23, ovulation was inhibited, whereas in sham-operated animals it was not. Estradiol benzoate (EB) injected sc at the time of unilateral ovariectomy significantly restored ovulation in immature rats primed with 3 IU PMS; progesterone was ineffective. These findings suggest that the endogenous estrogen level affects compensatory ovulation, and unilateral ovariectomy inhibits ovulation in the 22-day-old rat model by reducing the quantity of estrogen available for positive feedback.
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