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-bo rder membrane vesicles is markedly increased by short-term consumption of iron-deficient diet with no additional enhancement as the animal b ecomes functionally iron-deficient with continuing dietary Fe deprivat ion. In addition, we investigated whether previously observed in vivo absorption interactions of iron, zinc, and manganese occur in the brus h border membrane vesicles uptake process, and whether short-term or l ong-term consumption of an iron-deficient diet affects the interaction at the uptake level. We did not observe any differences in Fe+2 uptak e between normal and iron-deficient brush border membrane vesicles, ev en when the iron status contrast was intensified by feeding a high iro n versus iron-deficient diet for 3 weeks. Equimolar Zn+2 and Mn+2 decr eased Fe+2 uptake by 29 to 50% and II to 39%, respectively. Iron defic iency did Plot alter these effects. Equimolar Fe+2 decreased Zn+2 upta ke by 13 to 22%. Calcium, included as a negative control, did not affe ct Fe+2 uptake. Thus, some competition between Fe+2 and similar divale nt cations does occur at the level of the brush border membrane; the e xact nature of this competition remains to be determined