Inhibition of Ovulation and Associated Histological Changes. ∗

Abstract

The idea that the corpus luteum is responsible for the inhibition of ovulation seems to have been first elaborated by Beard 1 and by Prenant. 2 The experimental proof of the inhibitory action of the corpus luteum has been attacked in many different ways. The two most general methods have been based on anatomical and physiological modifications of the reproductive tract, correlated with the presence or absence of a functional corpus luteum, and, changes produced by the injection of extracts of lutein tissue. Corner and Hurni 3 reported negative results in an attempt to inhibit ovulation by injecting corpus luteum extracts in normal white rats. Loeb 4 failed to obtain consistent positive results in the guinea pig, while Papanicalaou 5 recently reported inhibition of ovulation in the same animal. Pearl and Surface 6 were able to stop hens from laying by injections of water extracts of a dried commercial preparation. Kennedy 7 described positive results on the rabbit for extracts made from a desiccated commercial preparation which were injected for a period of time before mating, resulting in the inhibition of ovulation. Parkes and Bellerby 8 reported inhibition of ovulation in mice by injections of an emulsion of an ether extract of the corpus luteum of the cow. They noted that not all of their extracts were potent, and that those that were soon deteriorated. Many different kinds of extracts have been employed by various investigators but the results obtained through their use are so contradictory that they cannot be discussed in this brief report.

An acid alcohol extract of the fresh corpus luteum of the sow has been prepared in this laboratory and refined to the extent that very little protein remains. This preparation is capable of sensitizing the uterus of spayed rats and guinea pigs so that placentomata may be produced (Weichert). 9 It will relax the pubic ligaments of virgin guinea pigs in oestrum (Hisaw)¹⁰; and will inhibit ovulation and oestrum in the normal female albino rat. Inhibition of oestrum was best effected by subcutaneous injections of an amount equivalent to 3 gm. of fresh tissue given every 4 or 5 hours from the beginning of oestrum until the experiment was ended. Rats injected in this manner did not come into oestrum for 6 to 12 days, the length of time for which ovulation was inhibited depending upon the amount of the extract injected. Attempts are now being made to inhibit ovulation for a greater period and to determine at what stage of the dioestrous interval injections may be most effective.