Increased maternofetal calcium flux in parathyroid hormone-related protein-null mice

H. Bond, M. R. Dilworth, B. Baker, E. Cowley, A. Requena Jimenez, R. D H Boyd, S. M. Husain, B. S. Ward, C. P. Sibley, J. D. Glazier

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The role of parathyroid hormone-related protein (PTHrP) in fetal calcium homeostasis and placental calcium transport was examined in mice homozygous for the deletion of the PTHrP gene (PTHrP-/- null; NL) compared to PTHrP+/+ (wild-type; WT) and PTHrP+/- (heterozygous; HZ) littermates. Fetal blood ionized calcium was significantly reduced in NL fetuses compared to WT and HZ groups at 18 days of pregnancy (dp) with abolition of the fetomaternal calcium gradient. In situ placental perfusion of the umbilical circulation at 18 dp was used to measure unidirectional clearance of 45Ca across the placenta in maternofetal (CaKmf) and fetoplacental (CaKfp) directions; CaKfp was <5% of Ca K mf for all genotypes. At 18 dp, CaKmf across perfused placenta and intact placenta (CaKmf(intact)) were similar and concordant with net calcium accretion rates in vivo. CaKmf was significantly raised in NL fetuses compared to WT and HZ littermates. Calcium accretion was significantly elevated in NL fetuses by 19 dp. Placental calbindin-D 9K expression in NL fetuses was marginally enhanced (P <0.07) but expression of TRPV6/ECaC2 and plasma membrane Ca2-ATPase (PMCA) isoforms 1 and 4 were unaltered. We conclude that PTHrP is an important regulator of fetal calcium homeostasis with its predominant effect being on unidirectional maternofetal transfer, probably mediated by modifying placental calbindin-D 9K expression. In situ perfusion of mouse placenta is a robust methodology for allowing detailed dissection of placental transfer mechanisms in genetically modified mice. © 2008 The Authors. Journal compilation © 2008 The Physiological Society.
    Original languageEnglish
    Pages (from-to)2015-2025
    Number of pages10
    JournalJournal of Physiology
    Volume586
    Issue number7
    DOIs
    Publication statusPublished - 1 Apr 2008

    Keywords

    • Animals
    • physiology: Biological Transport
    • metabolism: Calcium
    • metabolism: Calcium-Binding Protein, Vitamin D-Dependent
    • Female
    • metabolism: Fetus
    • physiology: Homeostasis
    • Male
    • physiology: Maternal-Fetal Exchange
    • Mice
    • Mice, Knockout
    • genetics: Parathyroid Hormone-Related Protein
    • metabolism: Placenta
    • physiology: Placental Circulation
    • Pregnancy
    • metabolism: Pregnancy, Animal

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