title: Inhibitory effect of calcium on non-heme iron absorption may be related to translocation of DMT-1 at the apical membrane of enterocytes.
abstract: Many studies show that calcium reduces iron absorption from single meals, but the underlying mechanism is not known. We tested the hypothesis that calcium alters the expression and/or functionality of iron transport proteins. Differentiated Caco-2 cells were treated with ferric ammonium citrate and calcium chloride, and ferritin, DMT-1, and ferroportin were quantified in whole-cell lysate and cell-membrane fractions. Calcium attenuated the iron-induced increase in cell ferritin levels in a dose-dependent manner; a significant decrease was seen at calcium concentrations of 1.25 and 2.5 mM but was only evident after a 16-24 h incubation period. Calcium and iron treatments decreased DMT-1 protein in Caco-2 cell membranes, although total DMT-1 in whole cell lysates was unchanged by either iron or calcium. No change was seen in ferroportin expression. Our data suggest that calcium reduces iron bioavailability by decreasing DMT-1 expression at the apical cell membrane, thereby downregulating iron transport into the cell.
authors.affiliation: School of Medicine, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: Ben A V
authors.initials: BA
authors.lastname: Thompson
authors.forename: Paul A
authors.initials: PA
authors.lastname: Sharp
authors.forename: Ruan
authors.initials: R
authors.lastname: Elliott
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Fairweather-Tait
mesh_terms: D001692:Biological Transport; D018938:Caco-2 Cells; D002118:Calcium / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D015536:Down-Regulation; D020895:Enterocytes / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption; D007501:Iron / Q000378:metabolism*; D021381:Protein Transport; D000098742:Ferroportin; D000099236:Solute Carrier Family 11, Member 2
chemical_list: D002118:Calcium; D027682:Cation Transport Proteins; D007501:Iron; D000098742:Ferroportin; D000099236:Solute Carrier Family 11, Member 2