IDENTIFICATION OF SPECIFIC RELAXIN-BINDING CELLS IN THE HUMAN FEMALE

Relaxin is secreted during pregnancy, but it has no verified effects i n humans. The objective of the present study was to identify the cells containing specific relaxin-binding sites in the uterine cervix, vagi na, uterus, mammary glands, mammary nipples, and term placenta in the human. The uterine cervix, vagina, and uterus were obtained from hyste rectomy specimens. Mammary glands and nipples were obtained after modi fied radical mastectomy. Placenta was obtained after normal delivery. Tissue samples were cut into slices (0.5-3 cm(3)), frozen in liquid ni trogen, and cryosectioned (8 mu m). Cells that bind relaxin were ident ified by sequential application of biotinylated porcine relaxin probe, antibiotin immunoglobulin G conjugated to 1 nm colloidal gold, and si lver enhancement for signal amplification. Relaxin bound with specific ity to epithelial cells, smooth muscle cells, and blood vessels in the cervix, vagina, uterus, and mammary nipples; to epithelial cells and blood vessels in the mammary glands; and to skin of the mammary nipple s. In addition, relaxin bound to individual cell types within the term placenta (amnion epithelium, syncytiotrophoblasts, blood vessels), an d to sebaceous glands within the nipples, We conclude that the specifi c relaxin-binding cells probably contain relaxin receptors. Identifica tion of putative relaxin receptors may provide insight into physiologi cal and/or therapeutic roles of relaxin in the human.