DIETARY CITRATE AND KIDNEY-FUNCTION AFFECT ALUMINUM, ZINC AND IRON UTILIZATION IN RATS

Four studies were conducted to examine the effect of dietary citrate and calcium and modest reductions in kidney function on aluminum utilization in rats. Ingestion of citrate increased retention of aluminum in bones of rats fed 1 mg Al/g diet and increased apparent absorption of zinc. The increased retention of aluminum was not linearly related to dietary citrate levels. These data suggest that citrate had a general effect on the solubility of trace elements in the gut that promoted absorption. When dietary calcium intake was increased from 67 to 250-mu-mol/g diet, aluminum concentrations in bone were reduced without a change in growth of rats. A reduction (approximately 30%) in kidney function, which was insufficient to alter growth, increased aluminum retention in bone by 34% in rats injected with aluminum and by 13% in rats fed aluminum. Rats fed aluminum seemed to retain in tissues only 0.01 to 0.05% as much aluminum as those injected with aluminum. Thus, tissue concentrations of aluminum, and presumably toxicity, can be altered by moderate changes in diet and kidney function even through overall retention of orally administered aluminum is extremely low.