IMMUNOCYTOCHEMICAL LOCALIZATION OF NONLUTEAL OVARIAN RELAXIN

Relaxin has been demonstrated to be produced by the corpus luteum of t he menstrual cycle and pregnancy and is also produced by the endometri um and decidua, although these nonluteal sources may not contribute to circulating relaxin concentrations. The reports of luteal production of relaxin have failed to consider nonluteal ovarian sources. To look for sources of nonluteal ovarian relaxin, human ovaries were collected from patients who underwent removal of the ovary for a variety of rea sons. Tissues were fixed in formalin and embedded in paraffin. Two mon oclonal antibodies were used for immunocytochemical staining, one dire cted against human relaxin and the other against the C peptide of pror elaxin. In addition to the expected staining of corpora lutea, the lut einized theca interna but not granulosa of developing follicles from o varies with an active corpus luteum of the cycle also stained positive for both relaxin and prorelaxin. Ovaries from term pregnant women wit h luteinized theca also demonstrated staining for relaxin and prorelax in. In addition to luteal and thecal cell staining, small clusters of pseudodecidual cells in the periphery of the ovary stained positive fo r relaxin and prorelaxin. These data indicate that the ovary contains theca interna-derived structural elements in addition to the corpus lu teum that produce relaxin when a corpus luteum is active, while granul osa-derived elements do not. This suggests that luteal production of r elaxin is from theca-derived elements and may explain instances of ind ependent relaxin and progesterone secretion.