Antigonadotropic effect of oxytocin on the isolated human corpus luteum

From each of 43 women who had gynecologic laparotomy at different and well-classified stages of the luteal phase of the cycle, the corpus luteum (CL) was excised, cut into pieces, and incubated for short time periods (30 to 240 minutes). Incubations were performed in the absence and presence of human chorionic gonadotropin (hCG) and different concentrations of oxytocin ([OT], 0.1 to 1000 mIU/ml). After incubation, the tissue levels of cyclic adenosine 3',5'-monophosphate (cAMP) and the media concentrations of progesterone (P) were determined. Although hCG stimulated both cAMP and P formation in CL of all ages, OT alone had no effect on the basal production of these parameters. However, under certain experimental conditions, OT counteracted the stimulatory effect of hCG on both cAMP and P formation. Because the maximal antigonadotropic effect was found for concentrations of OT in the magnitude of the physiologic intraluteal concentration, these in vitro data suggest a role for OT in the luteolytic process of humans.