Is Ovulation Alone Sufficient To Cause Formation of Corpora Lutea?

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Abstract
The release of LH, FSH and a luteotrophic substance from the pituitaries of nonpregnant gilts was blocked by continuous feeding of 500 mg/day of Repromix (a progestogen) for 16 days before and during the formation of ovulable follicles. Four consecutive daily injections of PMS induced the formation of follicles of ovulable size and these were caused to ovulate with a single injection of HCG given 24 hr after the last PMS injection. Repromix feeding was continued until the day of autopsy, which was 9 days after the injection of HCG. At autopsy, corpora lutea normal in morphologic appearance and progesterone concentration (48.8 μg/g luteal tissue) were present. A single injection of HCG into “pituitaryblocked” pregnant gilts could not overcome the Repromix-induced regression of the corpora lutea of pregnancy. Daily injections of HCG from the first day of pituitary blockade (day 25 of pregnancy) until the day of autopsy, 10 or 16 days later, appeared to maintain the weight of the corpora lutea but could not maintain the concentration of luteal progesterone. Since HCG can cause ovulation of follicles and the formation and maintenance of corpora lutea for 9 days after the single injection of HCG, but cannot overcome the luteolytic effect of Repromix in pregnant pigs, it is concluded that, in the normal nonpregnant gilt, a single release of an LH or luteotrophic substance, or both, can cause ovulation and the formation and maintenance of the corpora lutea of the estrous cycle. (Endocrinology74: 14, 1964)

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