Relationship of Developmental Stage to Regression of the Corpus Luteum in Swine1

Abstract

When corpora lutea are induced in an ovary that contains corpora lutea formed at the last previous estrus, regression of the 2 groups of corpora lutea is not simultaneous but, instead, the induced corpora lutea regress approximately one cycle length following formation. Pituitary FSH or a combination of PMS and HCG was administered to 27 female swine to induce ovulation during the luetal phase of the estrous cycle. Development and persistence of induced corpora lutea concurrent with regression of spontaneous corpora lutea were observed in 19 of 22 animals. These results demonstrate a selective regression of luteal tissue in swine that appears to be at least partially dependent on the age of the corpus luteum, i.e., the interval from ovulation to the onset of retrogressive changes during the nonfertile cycle. Concurrent maintenance of both spontaneously formed and induced corpora lutea was observed in 5 animals following hysterectomy. (Endocrinology74: 355, 1964)