Fetal parathyroids are not required to maintain placental calcium transport

AUTOR(ES)

Kovacs, Christopher S.

FONTE

American Society for Clinical Investigation

RESUMO

We used Hoxa3 knockout mice and other mouse models to study the role of the fetal parathyroids in fetal calcium homeostasis. Hoxa3-null fetuses lack parathyroid glands, and absence of parathyroid hormone (PTH) was confirmed with a rodent PTH immunoradiometric assay. The ionized calcium level of Hoxa3-null fetuses was significantly lower than that of wild-type or heterozygous littermates or of the mother. Both the rate of placental calcium transfer and the plasma PTHrP level were normal in Hoxa3 mutants and their heterozygous siblings. Because we had previously observed an increase in placental calcium transfer in PTH/PTHrP receptor 1–null (Pthr1-null) fetuses, we assayed plasma PTHrP in those mice. Pthr1-null fetuses had plasma PTHrP levels 11-fold higher than those of their littermates. Northern analysis, immunohistochemical, and in situ hybridization studies of Pthr1-null fetuses indicated that liver and placenta had increased expression of PTHrP. In summary, loss of fetal parathyroids in Hoxa3-null fetuses caused marked hypocalcemia but did not alter placental calcium transfer or the circulating PTHrP level. The findings in the Pthr1-null fetuses indicate that several tissues may contribute to the circulating PTHrP level in fetal mice.

Documentos Relacionados

• Regulation of murine fetal-placental calcium metabolism by the calcium-sensing receptor.
• Trienoic Fatty Acids Are Required to Maintain Chloroplast Function at Low Temperatures1
• Parathyroid hormone-related peptide (PTHrP) regulates fetal–placental calcium transport through a receptor distinct from the PTH/PTHrP receptor
• Calcium transport across the isolated dually perfused human placental lobule.
• Pregnant mice are not primed but can be primed to fetal alloantigens.