Stimulation in Vitro by 1,25-Dihydroxy-Vitamin D 3 of Intestinal Cell Calcium Uptake and Calcium-Binding Protein

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Abstract
Treatment of duodenal tissue from rats deficient in vitamin D with 1,25-dihydroxy-vitamin D 3 [1,25-(OH) 2 -D 3 ] led to more than a doubling of calcium uptake by the isolated cells and the appearance in those cells of previously undetectable calcium-binding protein (CaBP). Treatment with the precursor, 25-hydroxy-vitamin D 3 , was without effect on calcium uptake or CaBP. Cells from vitamin D-replete animals took up three and a half times more calcium than cells from deficient animals. This rapid (90-minute) effect of in vitro treatment with a physiological dose (4.7 × 10 -8 M ) of 1,25-(OH) 2 -D is the first such report and is in accord with the regulatory role of the hormone-like sterol.