Effect of Hypophysectomy During Early Proestrus on Ovulation in the Rat.

Hypophysectomy of adult female rats within 2 hours after the beginning of proestrus prevents ovulation from occurring within a 46-hour postoperative interval. Sham hypophysectomy does not prevent ovulation as shown by the presence of partially developed corpora lutea and tubal ova. It is concluded that a hypophyseal hormone (LH) is required for ovulation and luteinization in the rat and that the quantity of hormone needed to produce ovulation and luteinization is secreted subsequent to early proestrus.