Biology of Reproduction, Vol 25, 989-996, Copyright © 1981 by Society for the Study of Reproduction

Effect of Hypophysectomy on Atresia of Rat Preovulatory Follicles

¹ Department of Hormone Research, The Weizmann Institute of Science, Rehovot, 76100, Israel

Atresia of Graafian follicles was induced by hypophysectomy on the morning of the day of proestrus. As early as 6 h after hypophysectomy, follicles showed a reduced ability to respond with ovulation to administration of hCG, and 12 h after hypophysectomy all the follicles failed to ovulate. At 24 h after hypophysectomy, the follicles exhibited morphological changes characteristic of early atresia followed by advanced atresia at 48 h after the operation. Steroidogenesis in vitro of follicles from hypophysectomized rats was compared with that of sham-operated controls. The mean ± SEM rate of accumulation (ng/follicle/24 h) of progesterone, testosterone, and estradiol-17 was 5.1 ± 0.9, 6.3 ± 0.5, and 20.2 ± 3.7, respectively, in control follicles; 12 h after hypophysectomy progesterone accumulation was 22.7 ± 4.9, testosterone 4.5 ± 0.4, and estradiol-17 11.7 ± 0.9; and 48 h after the operation accumulation was 59.3 ± 8.3, 1.0 ± 0.3, and 0.10 ± 0.02, respectively. Thus atretic follicles from hypophysectomized rats are characterized by increased progesterone and decreased androgen and estradiol-17 production. Addition of LH to the culture medium stimulated progesterone accumulation in follicles from rats up to 24 h after hypophysectomy but not 48 h after the operation. It appears, therefore, that follicles gradually lose their responsiveness to LH during the atretic process.

Note:
ACKNOWLEDGMENTS We thank the NIAMDD for generous supply of gonadotropin preparations; Mrs. A. Tsafriri for skillful technical assistance; and Mr. S. Yosef for devoted care of the animals. We are indebted to Drs. D. J. Dierschke and A. Nimrod for their constructive criticism during the preparation of the manuscript. The contribution of R.H.B. constitutes part of the requirements for the Ph.D. degree of the Feinberg Graduate School of the Weizmann Institute of Science. The work was generously supported by the Ford Foundation and the Rockefeller Foundation.

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