Stimulation in vitro by 1,25-dihydroxy-vitamin D3 of intestinal cell calcium uptake and calcium-binding protein.

Treatment of duodenal tissue from rats deficient in vitamin D with 1,25-dihydroxy-vitamin D3 [1,25-(OH)2-D3] led to more than a doubling of calcium uptake by the isolated cells and the appearacne in those cells of previously undetectable calcium-binding protein (CaBP). Treatment with the precursor, 25-hydroxy-vitamin D3, 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 X 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.