Evidence for in vivo upregulation of the intestinal vitamin D receptor during dietary calcium restriction in the rat

M. J. Favus, D. J. Mangelsdorf, V. Tembe, B. J. Coe, M. R. Haussler

Research output: Contribution to journalArticle

62 Scopus citations

Abstract

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] increases intestinal calcium absorption through events that include binding of 1,25(OH)2D3 to the intracellular vitamin D receptor. In vitro studies using mammalian cell cultures reveal an increase in vitamin D receptor content after exposure to 1,25(OH)2D3. To test the hypothesis that 1,25(OH)2D3 increases enterocyte vitamin D receptor content in vivo, male rats were fed either a normal calcium diet (NCD, 1.2% Ca) or low calcium diet (LCD, 0.002% Ca). After 21 d LCD increased serum 1,25(OH)2D3 levels (27 ± 3 vs. 181 ± 17 pg/ml, P < 0.001) and increased transepithelial mucosal to serosal calcium fluxes (J(ms)) across duodenum (65 ± 21 vs. 204 ± 47 nmol/cm2·h, NCD vs. LCD, P < 0.01) and jejunum (23 ± 3 vs. 46 ± 4, P < 0.007). No change in serosal to mucosal calcium fluxes (J(sm)) were observed. LCD increased 1,25(OH)2D3 receptor number threefold in duodenum (32.9 ± 6.7 vs. 98.7 ± 13.7 fmol 1,25(OH)2D3/mg protein) and jejunum (34.1 ± 9.5 vs. 84.9 ± 7.7) without a change in the receptor affinity for 1,25(OH)2D3 (K(d)) is 0.17 ± 0.06 vs. 0.21 ± 0.02 nM for NCD and LCD duodenum, respectively). Duodenal polyadenylated vitamin D receptor mRNA determined by Northern blot analysis did not increase appreciably during LCD, suggesting that upregulation in vivo may not be due primarily to increased receptor synthesis. The results of this study indicate that under physiologic conditions as during chronic dietary calcium restriction, increased intestinal vitamin D receptor content accompanies increased calcium active transport. Upregulation of the vitamin D receptor by 1,25(OH)2D3 may result primarily from post-translational processes that decrease degradation of the receptor with increased receptor synthesis responsible for a negligible portion of the accumulation.

Original languageEnglish (US)
Pages (from-to)218-224
Number of pages7
JournalJournal of Clinical Investigation
Volume82
Issue number1
StatePublished - 1988

    Fingerprint

ASJC Scopus subject areas

  • Medicine(all)

Cite this