Placental transfer of parathyroid hormone

We investigated the in vitro transfer of three parathyroid hormone (PTH) fragments (amino acids 35-84, 44-68 and 65-84) through human placenta at term. The perfused and transferred fragments were measured radioimmunologically and identified by three different methods: high-pressure-liquid chromatography (HPLC), preparative flat-bed electrofocusing (PEGG), and gel filtration (GF). The study demonstrated that PTH fragments traverse the human placenta. The transferred and perfused fragments were identical. We observed a significant degradation of the perfused hormone during the passage through the placenta in both fetal and maternal directions. In addition, we measured the PTH concentrations on forty samples of maternal and umbilical cord artery and vein plasma obtained immediately after delivery. A highly significant correlation of PTH concentrations in the maternal and umbilical cord vessels was observed. These findings support the contention that human placenta at term is permeable for PTH fragments.