Production and biologic action of relaxin within the ovarian follicle: an overview.

The studies described here support the concept that relaxin is a product of the ovarian follicle and interacts with systemic hormones in the local regulation of the ovary. This report reviews the work indicating that relaxin is a product of the ovarian follicle and presents evidence for the biologic action of relaxin within the follicle. Production of relaxin by cells of the theca interna was given support by immunocytochemical localization work, in vitro production studies, and detection of relaxin mRNA by in situ hybridization. The relaxin content of porcine follicular fluid was shown to increase with development induced by gonadotropins. During thecal cell culture, luteinizing hormone and porcine follicular fluid increased relaxin secretion, whereas the presence of granulosa cells was without effect. A biologic action for relaxin on connective tissue remodeling was supported by an increase in follicle-stimulating hormone-stimulated plasminogen activator activity by granulosa cells. Additional work is needed to investigate the possibility of other roles for relaxin within the follicle, to identify relaxin receptors, and to explore the interaction of relaxin with endocrine and other paracrine factors in the ovary.