Short- and long-term effects of hypophysectomy and unilateral ovariectomy on ovarian follicular populations in sheep

Abstract

The effects of hypophysectomy and unilateral ovariectomy on the total number of follicles with > 3 layers of granulosa cells were determined at 4 and 70 days following treatment. The population of preantral follicles (< 0.23 mm diameter) was under gonadotropin control, but such control was only evident on a long-term basis. At 70 days after unilateral ovariectomy there was a large increase in the number of preantral follicles but at 70 days after hypophysectomy there was a large decrease. The population of antral follicles (> 0.23 mm diameter) was under the immediate control of gonadotropins. By 4 days after hypophysectomy all large antral follicles had become atretic and the number of antral follicles was further decreased at 70 days after treatment. At 70 days after unilateral ovariectomy there was an increase in the number of antral follicles. The follicular growth rates at 70 days following treatment were decreased in hypophysectomized ewes but increased in ewes after unilateral ovariectomy.