The absorption of dietary calcium is variable and incomplete. The efficiency of absorption is regulated to meet skeletal mineral requirements and is also sensitive to dietary calcium intake and circulating levels of 1, 25-dihydroxyvitamin D3 (1, 25(OH)2D3). The events involved in the translocation of calcium across the epithelium from lumen to blood have been studied using a variety of in vivo and in vitro techniques. The results permit construction of a two-component model for calcium transport composed of a transcellular pathway regulated by 1, 25(OH)2D3 and a paracellular pathway sensitive to transepithelial osmotic and electrochemical gradients. This review will focus on the pathways for calcium transport, the driving forces involved, and regulation by 1, 25(OH)2D3. Events at the cellular level, while poorly understood, will also be discussed.
KeywordsDietary Calcium Calcium Transport Dietary Calcium Intake Intestinal Calcium Absorption Paracellular Pathway
Unable to display preview. Download preview PDF.
- 1.LH Allen, Calcium bioavailability and absorption: a review, Am. J. Clin. Nutrition 35:783 (1982).Google Scholar
- 13.RH Wasserman and JS Chandler, Molecular mechanisms of intestinal calcium absorption, in: “Bone and Mineral Research,” WA Peck, ed., Elsevier Science Publishers, Amsterdam (1985).Google Scholar
- 14.HF DeLuca, The vitamin D story: a collaborative effort of basic science and clinical medicine, FASEB 2:224 (1988).Google Scholar
- 18.MJ Favus, DJ Mangelsdorf, V Tembe, BJ Coe, and MR Haussler, Evidence for in vivo up-regulation of the intestinal vitamin D receptor during dietary calcium restriction in the rat, J. Clin. Invest. In press (1988).Google Scholar