EXPRESSION OF PARATHYROID HORMONE-RELATED PROTEIN AND ITS RECEPTOR INHUMAN UMBILICAL-CORD - EVIDENCE FOR A PARACRINE SYSTEM INVOLVING UMBILICAL VESSELS

OBJECTIVE: Our purpose was to study the expression and localization of parathyroid hormone-related protein and expression of the parathyroid hormone/parathyroid hormone-related protein receptor in human umbilic al cord. STUDY DESIGN: The expression and localization of parathyroid hormone-related protein and expression of the parathyroid hormone/para thyroid hormone-related protein receptor were studied in isolated tiss ues from the human umbilical cord by Northern analysis, reverse-transc riptase polymerase chain reaction, Southern gel analysis, and immunolo calization procedures at the light and electron microscopic levels. RE SULTS: Parathyroid hormone-related protein was abundantly expressed in the umbilical cord. Immunohistochemical and immunocytochemical techni ques confirmed hormone localization in the amnion epithelial layer and in vascular smooth muscle and endothelial cells in vessels from the u mbilical cord and placental chorionic plate. Multiplex reverse-transcr iptase polymerase chain reaction identified expression of receptor mes senger ribonucleic acid in vessels of the umbilical cord; this finding was verified by means of Southern gel analysis of the products of the reverse-transcriptase polymerase chain reaction. CONCLUSION: A parath yroid hormone-related protein paracrine system appears to exist in hum an umbilical cord. We suggest that it may be involved in the control o f fetal placental circulation.