The occurrence of relaxin in hyperstimulated human preovulatory follicles collected in an in vitro fertilization program.

The avidin-biotin immunoperoxidase method and antisera against highly purified porcine relaxin were utilized to localize relaxin-like immunoreactivity in biopsied specimens from six preovulatory follicles from four women undergoing laparoscopy for oocyte retrieval in an in vitro fertilization program. By histological criteria, three of the follicles were luteinized and three were not. Relaxin was found in the granulosa cells of those cells which showed histological luteinization, whereas no relaxin was found in the nonluteinized preovulatory follicles. Our results show, for the first time, the occurrence of relaxin in the human ovary before ovulation and they suggest that the appearance of relaxin is related to the luteinization process.