title: Vitamin D-regulated calcium transport in Caco-2 cells: unique in vitro model.
abstract: The human colon adenocarcinoma cell line Caco-2 is the only intestinal cell line to differentiate spontaneously in culture exhibiting structural and biochemical characteristics of mature enterocytes and to possess a vitamin D receptor in the fully differentiated state. Transepithelial calcium transport was characterized in differentiated Caco-2 cells grown on permeable filters supports to assess the potential utility of this cell line as an in vitro model to study 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]-induced calcium transport. Calcium transport was increased in a dose-dependent manner by 1,25(OH)2D3. Total calcium transport at different calcium concentrations could be fitted to a modified Michaelis-Menten equation containing a linear transport component. The maximum rate of saturable calcium transport was increased by 4.3-fold (P less than 0.005) in cells treated with 10(-8) M 1,25(OH)2D3. This treatment also increased the apparent buffer calcium concentration that results in half-maximal velocity from 0.4 to 1.3 mM but had no significant effect on nonsaturable calcium transport. Caco-2 cells grown on permeable filter supports provide a unique in vitro human cell culture model to study the mechanism of vitamin D-regulated transepithelial intestinal calcium transport.
authors.affiliation: United States Department of Agriculture, Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts 02111.
authors.forename: A R
authors.initials: AR
authors.lastname: Giuliano
authors.forename: R J
authors.initials: RJ
authors.lastname: Wood
mesh_terms: D000230:Adenocarcinoma; D001692:Biological Transport / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003110:Colonic Neoplasms; D004305:Dose-Response Relationship, Drug; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007444:Inulin / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological
chemical_list: D007444:Inulin; D002117:Calcitriol; D002118:Calcium