Iron uptake by isolated intestinal brush borders: changes induced by alterations in iron stores.

Abstract

Abstract Recent studies have indicated that intestinal brush borders and their component microvilli are important in the digestion and absorption of various nutrients. In the present investigation studies were carried out to define more clearly the role of intestinal brush borders in iron transport. Brush borders were prepared from villous absorptive cells isolated from the proximal 20 cm. and distal 50 cm. of rat small intestine. Electron microscopic studies and determination of sucrase activity in representative brush border pellets indicated that a highly pure preparation of brush borders was achieved. The binding of ferrous iron to brush borders was not affected by removal of oxygen or glucose from the incubation medium. However, such binding was found to be temperature dependent. These observations indicate that attachment of iron to brush borders does not depend on an energy-requiring process and probably results from adsorption. It was demonstrated that: (1) Proximal brush borders take up significantly greater quantities of ferrous iron than ileal brush borders; (2) the uptake of iron by proximal brush borders can be depressed by prior iron-loading; and (3) the uptake of iron by ileal brush borders can be increased by prior iron-depletion. That the uptake of iron by brush borders can be modified by altering the iron stores of the animal suggests that the brush border may participate in the regulation of intestinal iron transport.