The Effect of Gonadotropic Hormones on the Persisting Corpora Lutea in Hypophysectomized Rats1

In a previous communication (1) it was shown that complete involution of the persisting corpora lutea in hypophysectomized adult rats could be brought about by the injection of the luteinizing hormone (LH) over a period of 10 days. Injections of estrogen, progestin or the follicle-stimulating hormone (FSH) of the hypophysis had no demonstrable effect on these structures. This report will present the results obtained in a further study of the separate and combined action of pituitary FSH and LH and the urinary gonadotropic hormones on the ovaries of hypohysectomized adult rats. Special attention has been given to the behavior of the follicular mechanism, the histological changes in the persisting corpora lutea and the physiological activity of the ovaries as determined by changes in the vaginal smear, the size and appearance of the uteri and the ability to develop placentomata. Adult virgin female rats were treated with unfractionated pituitary extracts for 5 days prior to the removal of the pituitary gland. A postoperative delay of 10 to 25 days (usually 15) was allowed before any subsequent injections were begun. Fifteen days proved to be sufficient time to allow for involution of all the antra-containing follicles, to establish the fact that the corpora lutea were persisting, and to permit treatment of the animal before cachexia had become unduly severe. Thus the standard experimental animals have been hypophysectomized female rats in which the entire reproductive tracts had become atophic and large persisting corpora lutea plus a few nonantra containing follicles remained in the ovary (fig. 3).