beta-carotene and inhibitors of iron absorption modify iron uptake by Caco-2 cells

A National fortification program instated in Venezuela in 1993 reduced iron deficiency and anemia by half in only 1 y. The fortification mixture conta ined ferrous fumarate, vitamin A and other vitamins. We conducted experimen ts to characterize ferrous fumarate uptake by Caco-2 cells. Increasing amou nts of ferrous fumarate, vitamin A, phytate, tannic acid and beta-carotene were added to incubation mixtures using a range of concentrations that incl uded the molar ratios used in the Venezuelan fortification program. Cells w ere incubated for 1 h at 37 degrees C with 37 kBq Fe-59 and the compound to be evaluated. They were then rinsed, trypsinized and counted to measure up take. Effects of ascorbic acid, days in culture and use of flasks or insert s were also evaluated. Optimal conditions for uptake experiments were pH 5. 5, in the presence of ascorbic acid and at 16 d in culture. Use of flasks o r inserts did not affect uptake. Vitamin A did not significantly increase i ron uptake under the experimental conditions employed. However, beta-carote ne (6 mu mol/L) significantly increased iron uptake compared to no beta-car otene addition (114.9 +/- 6.3 and 47.2 +/- 5.9 pmol/mg cell protein, respec tively). Moreover, in the presence of phytates or tannic acid, beta-caroten e generally overcame the inhibitory effects of both compounds depending on their concentrations. We conclude that beta-carotene improves iron uptake a nd overcomes the inhibition by potent inhibitors of iron absorption. These experiments also validated the usefulness of Caco-2 cell model system to ev aluate iron metabolism.