|YEUNG, CHI KONG|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Review Article
Publication Acceptance Date: 8/7/2006
Publication Date: 9/9/2006
Citation: Zhu, L., Yeung, C., Miller, D., Glahn, R.P. 2006. Iron uptake by caco-2 cells from nafeedta and feso4: effects of ascorbic acid, ph, and a fe(ii) chelating agent. Journal of Agricultural and Food Chemistry. 54:7924-7928.
Technical Abstract: Sodium iron (III) ethylenediaminetetraacetate (NaFeEDTA) has considerable promise as an iron fortificant because of its high bioavailability in foods containing iron absorption inhibitors. In this study, uptakes of iron from NaFeEDTA, FeSO4 and FeCl3 by Caco-2 cells were compared in the absence or presence of ascorbic acid (AA), an iron absorption enhancer; at selected pH levels; and in the absence or presence of an iron absorption inhibitor, bathophenanthroline disulfonic acid (BPDS). Ferritin formation in the cells was used as the indicator of iron uptake. Uptake from all three Fe sources was similar in the absence of AA. Adding AA at a 5:1 molar excess compared to Fe increased uptake by 5.4-, 5.1-, and 2.8-fold for FeSO4, FeCl3, and NaFeEDTA, respectively. The smaller effect of AA on uptake from NaFeEDTA may be related to the higher solubility of NaFeEDTA, and/or the strong binding affinity of EDTA for Fe3+, which may prevent AA and Duodenal cytochrome b (Dcytb) from effectively reducing EDTA-bound Fe. Uptake was inversely related to the pH of the media over a range of 5.8 to 7.2. Since uptake by DMT-1 is proton-coupled, the inverse relationship between pH and Fe uptake in all three iron sources suggests they all follow the DMT-1 pathway into the cell. Adding BPDS to the media inhibited uptake from all three iron compounds equally. Since BPDS binds Fe2+ but not Fe3+ and since only Fe2+ is transported by DMT-1, the finding that BPDS inhibited uptake from NaFeEDTA suggests that at least some iron dissociates from EDTA and is reduced just as simple inorganic iron at the brush border membrane of the enterocyte. Taken together, these results suggest that uptake of iron from NaFeEDTA by intestinal enterocytes is regulated similarly to uptake from iron salts.