Effects of dietary supplementation with aluminum and citrate on iron metabolism in the rat

The metabolism of iron (Fe) has been shown to interact with that of aluminu m (Al) in relation to intestinal absorption, transport in the blood plasma, and the induction of lipid peroxidation and cellular damage. Also, dietary supplementation with citrate has been shown to increase the absorption of both metals and, in the presence of high intakes of Fe and Al, leads to exc essive accumulation of both metals in the body. In this study, the likely i nteraction between Al and internal Fe metabolism was investigated using rat s fed diets that were either deficient, sufficient, or loaded with Fe, with or without the addition of Al and sodium citrate. These diets commenced wh en the rats were 4 wk old and were continued for 9-11 wk. At that time, Fe metabolism as assessed by measurement of organ uptake of Fe-59 and I-125-tr ansferrin, after iv injection of transferrin labeled with both isotopes, pl us measurement of tissue concentrations of nonheme Fe and Al. The Fe-defici ent diet and Fe-loaded diet led to states of Fe deficiency and Fe overload in the rats, and supplementation of the diet with Al increased Al levels in the kidneys, Liver, and femurs, but, generally only when the diet also con tained citrate. Neither Al nor citrate supplementation of the diet had any effect on nonheme Fe concentrations in the liver, kidney, or brain, or on t he uptake of Fe-59 or I-125-transferrin by liver, kidney, brain, or spleen. Only with the femurs was a significant effect observed: increased Fe-59 up take in association with increased Al intake. Therefore, using this animal model, there was little evidence for interaction between Fe and Al metaboli sm, and no support was obtained for the hypothesis that dietary supplementa tion with Fe and citrate can lead to excessive Fe absorption and deposition in the tissues.