The Role of Parathyroid Hormone-Related Protein in Intra-Tracheal Fluid

Parathyroid hormone-related protein (PTHrP), a multi-functional protein, is produced by many tissues in fetus. PTHrP concentration in amniotic fluid is reported to be significantly higher than in either fetal or maternal plasma. Other investigators have reported that PTHrP in amniotic fluid is derived mainly from amnion. The aim of this study was to investigate the contribution of fetus to PTHrP in amniotic fluid and the role of PTHrP in human fetal lung tissue. Samples of amniotic fluid, neonatal intra-tracheal fluid, gastric fluid, and the first urine of neonates were obtained at the time of elective cesarean section (n=11), and the concentrations of PTHrP were measured. The PTHrP level in intra-tracheal fluid (41.0±19.6pmol/l, mean±SD) was significantly higher than the levels in amniotic fluid (22.1±0.8), neonatal gastric fluid (13.5±2.5), first urine (0.95±0.6), umbilical cord venous and arterial plasma (1.35±0.2, 1.63±0.3) and maternal plasma (1.05±0.1). PTHrP and PTH/PTHrP receptor mRNA were detected in human lung tissue obtained from a fetus stillborn at 36 weeks of gestation. The effects of PTHrP on fetal lung maturation were studied in H441 cells from a human lung epithelial cell line. PTHrP (10-7M) significantly suppressed cell proliferation (p