Gestational changes in Ca2+ transport across rat placenta and mRNA for calbindin(9K) and Ca2+-ATPase

J. D. Glazier, D. E. Atkinson, K. L. Thornburg, P. T. Sharpe, D. Edwards, R. D.H. Boyd, C. P. Sibley

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78 Scopus citations


The unidirectional maternofetal clearance (K(mf)) of 45Ca was measured across the rat placenta over the last one-third of gestation. K(mf) for 45Ca normalized to its diffusion coefficient in water (K(mf)/D(w)) increased 72-fold between days 15 and 22 of gestation from 3.5 ± 0.3 to 253.1 ± 22.0 cm/g placenta, respectively. At 15 and 18 days of gestation, K(mf)/D(w) for 45Ca was similar to K(mf)/D(w) for the paracellular marker [14C]mannitol, but at 21 and 22 days of gestation, K(mf)/D(w) for 45Ca was significantly higher than K(mf)/D(w) for [14C]mannitol, indicating that an additional route of transfer, other than diffusion, becomes available to calcium during this period. Northern hybridization analysis demonstrated that rat placental calbindin(9K)-to-β-actin mRNA ratio increased 135-fold between 15 and 22 days of gestation and was temporally associated with the gestational increase in K(mf)/D(w) for 45Ca. In contrast, rat placental Ca2+-ATPase-to-β-actin mRNA ratio increased only two- to threefold over the same gestational period and did not mirror the gestational changes in calcium clearance. These trends suggest that the expression of placental calbindin(9K), but not Ca2+-ATPase, may be rate limiting to placental calcium transport in the rat.

Original languageEnglish (US)
Pages (from-to)R930-R935
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number4 32-4
StatePublished - 1992
Externally publishedYes


  • calcium binding protein
  • calcium clearance
  • calcium pump
  • pregnancy

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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