DEFECTIVE IRON UPTAKE BY THE DUODENUM OF BELGRADE RATS FED DIETS OF DIFFERENT IRON CONTENTS

Homozygous Belgrade rats have an inherited hypochromic, microcytic ane mia that is due to impaired iron transport into immature erythrocytes. There is also evidence for abnormal iron transport in other tissues s uch as the intestine. This study was aimed at investigating the intest inal defect in rats that had been fed diets for 12 days that are norma l, low, or high in iron. The duodenal uptake, transfer and absorption of Fe(III)-nitrilotriacetate and Fe(II)-ascorbate were studied using i n vivo tied-off gut sacs in genetically normal rats and in heterozygou s or homozygous Belgrade rats. In normal and heterozygous Belgrade rat s, the handling of Fe(III) and Fe(II) was similar; uptake, transfer, a nd absorption of Fe(III) and Fe(II) changed inversely with the iron co ntent of the diet. In contrast, in homozygous Belgrade rats the uptake of both Fe(III) and Fe(II) was markedly reduced and absorption of Fe( III) did not change when animals were fed an iron-deficient diet. Sinc e absorption of Fe(II) was similar to Fe(III), there is no evidence th at the defect in iron absorption is due to failure of a mechanism for reduction of Fe(III). The lowered uptake of Fe(III) and Fe(II) in homo zygous Belgrade rats probably involves a defective iron carrier associ ated with the microvillous membrane of the duodenum.