FERROUS IRON UPTAKE BY RAT DUODENAL BRUSH-BORDER MEMBRANE-VESICLES - EFFECTS OF DIETARY IRON LEVEL AND COMPETING MINERALS (ZN+2, MN+2, AND CA+2)

We sought to confirm a recent report that Fe+2 uptake into mt brush-border membrane vesicles is markedly increased by short-term consumption of iron-deficient diet with no additional enhancement as the animal becomes functionally iron-deficient with continuing dietary Fe deprivation. In addition, we investigated whether previously observed in vivo absorption interactions of iron, zinc, and manganese occur in the brush border membrane vesicles uptake process, and whether short-term or long-term consumption of an iron-deficient diet affects the interaction at the uptake level. We did not observe any differences in Fe+2 uptake between normal and iron-deficient brush border membrane vesicles, even when the iron status contrast was intensified by feeding a high iron versus iron-deficient diet for 3 weeks. Equimolar Zn+2 and Mn+2 decreased Fe+2 uptake by 29 to 50% and II to 39%, respectively. Iron deficiency did Plot alter these effects. Equimolar Fe+2 decreased Zn+2 uptake by 13 to 22%. Calcium, included as a negative control, did not affect Fe+2 uptake. Thus, some competition between Fe+2 and similar divalent cations does occur at the level of the brush border membrane; the exact nature of this competition remains to be determined