1,25-Dihydroxyvitamin D3 inhibits Na+-dependent phosphate transport in osteoblastic cells

J. Green, K. V.Q. Luong, C. R. Kleeman, L. H. Ye, C. Chaimovitz

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6 Scopus citations

Abstract

In the present work we investigated the influence of vitamin D3 metabolites on Na+-dependent phosphate (P(i)) transport in the clonal osteoblastic cell line UMR-106. The vitamin D3 metabolite 1,25- dihydroxyvitamin D3 [1,25(OH)2D3] dose-dependently inhibited P(i) transport with a half-maximal concentration of ~5 x 10-11 M. The effect of 1,25(OH)2D3 was first observed after 8 h of preincubation period. Inhibition of phosphate uptake was relatively specific for the 1,25(OH)2D3 analogue of vitamin D3. The potency order was 1,25(OH)2D3 >> 24,25- dihydroxyvitamin D3 > 25-[3H]hydroxyvitamin D3. Kinetically, 1,25(OH)2D3 decreased the maximal velocity of the phosphate uptake system, whereas the affinity for phosphate was unaffected. Activation of protein kinase C (PKC) in UMR-106 cells stimulated Na+-dependent P(i) transport. Nonetheless, the inhibitory effect of 1,25(OH)2D3 on P(i) transport was not related to downregulation of PKC. Chemical determination of intracellular P(i) showed a 50% reduction after 24-h preincubation with 10-8 M 1,25(OH)2D3. We conclude that 1,25(OH)2D3 inhibits Na+-dependent phosphate transport in osteoblastic cells. This in turn leads to intracellular P(i) depletion. The physiological implication of this phenomenon on the effects of vitamin D on osteoblasts in situ is discussed.

Original languageEnglish
Pages (from-to)C287-C295
JournalAmerican Journal of Physiology - Cell Physiology
Volume264
Issue number2 33-2
DOIs
StatePublished - 1 Jan 1993
Externally publishedYes

Keywords

  • alanine
  • bone mineralization
  • collagen
  • protein kinase C
  • sodium-phosphate cotransport

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