The presence of vitamin D receptors in small intestine muscle cells may lead one to think that vitamin D may act locally, influencing intracellular calcium concentration and contributing to the contraction-relaxation regulation of the intestinal smooth muscle cells. This study investigates the potential effects of vitamin D and calcium on intestinal motility using an in vitro test.
Different calcium concentrations added to the tissue not pre-treated with 1,25-dihydroxycholecalciferol [1α,25(OH)2D3] produced no response at low doses (1.25 × 10−3 and 2.0 × 10−3 mol L−1) and only a very weak response at higher concentration (3.0 × 10−3 mol L−1). The addition of 1α,25(OH)2D3 (1.44 × 10−10 mol L−1) had no effect on isolated ileum motility. When calcium (3.0 × 10−3 mol L−1) was added after at least 3 hours, it evoked evident and persistent contractions for 60–90 minutes. The contractions were at about 40 % of the peak produced by acetylcholine. Thus, simultaneous intake of vitamin D and calcium might be a useful co-adjuvant in intestinal atony therapy aimed to stimulate normal gut motility in humans. These findings imply that supplemental vitamin D may be important in all cases where calcium has to be prescribed.