EXPRESSION AND SPECIFIC IMMUNOLOCALIZATION OF THE HUMAN PARATHYROID-HORMONE PARATHYROID HORMONE-RELATED PROTEIN-RECEPTOR IN THE UTEROPLACENTAL UNIT

OBJECTIVE: Our purpose in these studies was to determine the expressio n and cellular localization of the parathyroid hormone/parathyroid hor mone-related protein receptor in the human uteroplacental unit. STUDY DESIGN: Human uteroplacental tissues were obtained and ribonucleic aci d was extracted. Reverse transcriptase-polymerase chain reaction was p erformed with use of primers for both the parathyroid hormone/parathyr oid hormone-related protein receptor and human phosphoglyceraldehyde d ehydrogenase. Ethidium bromide-stained gels and Southern blots were ev aluated, and polymerase chain reaction fragments were sequenced. For i mmunohistochemistry, slides were incubated with a newly developed anti body (3D1.1) specific for the parathyroid hormone/parathyroid hormone- related protein receptor, and bound monoclonal antibody was detected b y use of the avidin-biotin technique. RESULTS: Reverse transcriptase p olymerase chain reaction gels and blots showed that receptor messenger ribonucleic acid was present in choriodecidua, placenta, and myometri um. Sequence analysis revealed complete identity of the receptor produ ct and the known nucleotide sequence in the receptor. There was intens e receptor staining of the myometrial smooth muscle as well as stainin g of the endothelium and smooth muscle of the associated vasculature. In umbilical cord immunoreactive receptor was found in the vascular en dothelium and vascular smooth muscle cells and in stromal cells. In ch oriodecidua receptor was found in chorionic trophoblasts and deciduali zed endometrial stromal cells. In all tissues immunostaining was speci fic, as evidenced by the blocking of staining after addition of recept or peptide to the antibody (absorbed controls). CONCLUSION: The parath yroid hormone/parathyroid hormone-related protein receptor is widely e xpressed in the human uteroplacental unit. The cellular localizations of the receptor in smooth muscle reflect the ability of parathyroid ho rmone-related protein to relax both uterine and vascular smooth muscle . The presence of novel autocrine and paracrine systems in the human u teroplacental unit is suggested by the finding that the same cells or adjacent cells produce both parathyroid hormone-related protein and it s receptor.