Role of redox systems on Fe3+ uptake by transformed human intestinal epithelial (Caco-2) cells.
Caco-2 cells were used as a model of human intestinal epithelium to investigate the role of redox systems in transepithelial transport of 59Fe3+. The cells reduced Fe3+ present in the apical medium; the reduction was 50% inhibited by adriamycin and p-chloromercuribenzoate. Addition of [14C]ascorbate to the basolateral medium resulted in accumulation of 14C radioactivity in both cells and apical medium; apical radioactivity increased with time and was probably caused by paracellular flux. The cells provided Fe3+ reduction capacity to the apical incubation medium. Addition of ascorbate to the basolateral medium increased this reduction capacity 2-fold and the cellular uptake of 59Fe3+ 1.8-fold. Adriamycin significantly inhibited both cellular 59Fe uptake and Fe transport into the basolateral side. The results indicate that Caco-2 cells reduce apical Fe3+ by two parallel mechanisms: by a plasma membrane ferrireductase and by the secretion of reductants of either cellular or basolateral origin. The data support a model for Fe3+ intestinal absorption in which cell-mediated Fe3+ reduction occurs before cellular Fe uptake.
Núñez
M T
MT
Department of Biology, Faculty of Sciences, University of Chile, Santiago.
Alvarez
X
X
Smith
M
M
Tapia
V
V
Glass
J
J
D001205:Ascorbic Acid / Q000378:metabolism; D001692:Biological Transport; D003110:Colonic Neoplasms / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D007501:Iron / Q000378:metabolism*; D010084:Oxidation-Reduction; D014407:Tumor Cells, Cultured
D007501:Iron; D001205:Ascorbic Acid