IRON STATUS AFFECTS ALUMINUM UPTAKE AND TRANSPORT BY CACO-2 CELLS

To study the cell biology of aluminum uptake and transport in intestinal epithelia, an in vitro system based on intestine-derived Caco-2 cells grown in bicameral chambers was used. Aluminum was offered on the apical surface of Caco-2 cell monolayers as either aluminum citrate, aluminum lactate or aluminum nitrilotriacetate at 1:2 molar ratios, and the aluminum uptake into the cells and transport into the basal chamber were measured. The kinetics of cellular uptake of aluminum were different for the three chelators, although with all three chelators a final cellular concentration of similar to 50 nmol/mg cell protein was achieved. The total transport of aluminum into the basal chamber was greater for aluminum citrate and aluminum nitrilotriacetate than for aluminum lactate, suggesting that the chelator may direct aluminum into compartments from which aluminum is more easily transported. The iron status of the Caco-2 cells significantly affected both cellular uptake and transport of aluminum. Both iron-depleted and iron-overloaded cells exhibited significantly lower aluminum transport than cells of normal iron status. Aluminum loading of the Caco-2 cells had adverse effects on Fe-59(2+) and Fe-59(3+) transport compared with that of normal cells. These findings suggest that the Caco-2 cell line grown in bicameral chambers provides a model for studying aluminum transport, that aluminum uptake and transport to the basal chamber were affected by the chelator used, and that aluminum uptake and transport pathways are similar to those of iron.