Concentration-dependent absorption of aluminum in rats exposed to labile aluminum in drinking water

The hypothesis was tested that the absorption of labile Al in rats will inc rease when the Al-binding capacity of food components in the stomach is sat urated. Male rats were exposed to 0, 10, 50, or 500 mg labile Al/L in acidi c drinking water (pH 3) for 9 wk. The results show that labile Al in drinki ng water is complexed by feed constituents in the stomach of the rat in viv o, thus causing a nondetectable absorption of Al at 10 mg Al/L. An increase d absorption of Al at 50 and 500 mg Al/L was associated with a saturation o f the Al-binding capacity of feed components in the lumen of the stomach, c ausing the appearance of labile Al. Thus, the presence of labile Al in drin king water does nor necessarily result in a high Al absorption when the wat er is ingested, since the bioavailability of labile Al is dependent both on the amount and composition of Al-binding components present in the gastroi ntestinal tract at the rime of ingestion of the water. it is thus not possi ble to predict the body burden of Al in humans just by measuring the Al con centrations in drinking water. Even a further refining of the exposure meas urement to include speciation of Al in the water may not markedly improve t he prediction of the Al body burden. Future epidemiological studies must th erefore be based on actual measurements of Al concentration in tissues or f luids from the study subjects.