Oestrin and Progestin Content of the Corpus Luteum of the Sow

Abstract

The oestrin and progestin content of the corpus luteum of the sow was determined at various stages of development. Ovaries were obtained fresh from the abattoir and separated into the following groups: 1, early corpora lutea up to about the sixth or seventh day from the time of rupture of the Graafian follicle; 2, fully formed corpora lutea representing the various stages of early and middle pregnancy; 3, degenerating corpora lutea, and 4, corpora albicans. This separation does not take into account the correlation of the development of the egg and embryo, since the large amounts of ovaries were primarily for the preparation of progestin. However this macroscopic separation demonstrated that there is variation in the level of progestin which has physiological significance. Due care was taken in the dissection of each batch of corpora lutea that follicular fluid was not a contaminant.

Progestin and oestrin were prepared and separated according to the method of Allen. 1 The progestin content was determined according to the method of standardization of Corner and Allen. 2 The oestrin level was obtained by the vaginal smear test using castrated female rats. The number of rabbit units of progestin and the number of rat units of oestrin per 100 gm. of corpora lutea are recorded in Table I.

It is to be noted that the progestin content is highest during the first 6 to 7 days. If the hemorrhage weight were not considered in the above, the level of progestin would be still higher since the hemorrhage which occurs in about 50% of the corpora lutea at this stage 3 increases the weight of the tissue. This high content of progestin correlates well with the active growth of the granulosa cell during this period. 3