FURTHER STUDIES OF THE FOLLICULAR-CORPUS LUTEUM HORMONE RELATIONSHIP IN THE RABBIT

Abstract

Experiments on 35 [female] rabbits showed definitely that a quantitative relationship exists between estrin and corporin (the corpus luteum hormone responsible for the progestational reaction) in the production of endometrical changes characteristic of early pregnancy. If estrin and corporin are injected simultaneously into castrate rabbits, the result to be expected depends on the higher dosage of either hormone and the apparent antagonism is explained on the basis of the 2 hormones competing physiologically for the endometrium. The estrous hormone can hold the action of injected corporin in abeyance for an ex- tended period (9 days at least) after which, if the dosage of estrin is lowered and corporin treatment continued, the effect of corporin becomes manifested. It takes many more times the amt. of estrin to obliterate the characteristic modification in the endometrium of early pregnancy than it does to overpower the effects of a rabbit unit of corporin capable of producing a histological picture equally good in a castrate animal. It takes slightly more corporin to produce a progestational modification in a non-castrate [female] rabbit in heat than it does to produce comparable change in the uterus of a rabbit castrated in heat and then treated. Corporin alone or with the addition of estrin does not seem able to maintain the progestational modification indefinitely. The amt. of corporin which in 5 days will produce a good progestational modification in a non-castrate rabbit in heat will not inhibit ovulation following the proper stimulation.