Induction of Superovulation in Acutely Hypophysectomized Rats and Presence of Ovulable Population of Follicles
1993 年 39 巻 2 号 p. 123-128
詳細
1993 年 39 巻 2 号 p. 123-128
Superovulation was induced in intact and acutely hypophysectomized mature rats by a successive eCG-hCG treatment. In the rats hypophysectomized after the onset of GTH surges, increment in eCG dosages maximized the number of ova shed by the following hCG treatment, and the maximum number was similar to those in non-hypophysectomized rats. In the rats hypophysecto-mized before GTH surges, however, the number of ova shed was significantly less, but this decrease was restored by an hCG injection immediately after the hypophysectomy. These results indicate that the maximum number of ova shed is determined by the limited number of eCG-responsive follicles that are generated during exposure to an antecedent LH surge. In intact rats, excess doses of eCG elicited enhanced progesterone secretion which, in turn, established PRL surges. These PRL surges appears to cause atretic changes in growing follicles and decreased the number of ova shed by the following hCG treatment. Thus, the upper limit of the number of ova shed in mature cycling rats subjected to the eCG-hCG treatment was estimated to be approximately 80.
