Bioavailability and intestinal absorption of aluminum in rats - Effects ofaluminum compounds and some dietary constituents

In the present investigation, the deposition of aluminum in intestinal frag ment and the appearance in blood were studied in a perfused rat intestine i n situ for 1 h with several aluminum forms (16 mM). We observed that alumin um absorption was positively correlated with the theoretic affinity of alum inum and the functional groups of the chelating agent. The absorption of al uminum after ingestion of organic compounds is more important than after in gestion of mineral compounds, with the following order: Al citrate > Al tar trate, Al gluconate, Al lactate > Al glutamate, Al chloride, Al sulfate, AZ nitrate. Absorption depends on the nature of the ligands associated with t he Al3+ ion in the gastrointestinal fluid. The higher the aluminum retentio n in intestinal fragment, the lower the absorption and appearance in blood. However, the higher aluminum concentration is always in the jejunal fragme nt because of the influence of pH variation on this fragment. Another objec tive of the present study was to determine the influence of several paramet ers on aluminum citrate absorption: with or without 0.1 mmol dinitrophenol/ L, with aluminum concen tration from 3.2, 16, 32, and 48, to 64 mmol/L, med ia containing 0, 3, or 6 mmol Ca/L, with or without phosphorus or glucose. It is concluded that aluminum is absorbed from the gastrointestinal tract b y (1) a paracellular energy independent and nonsaturable route, mainly used for high aluminum concentration, which is modified by extracellular calciu m, and (2) a transcellular and saturable route, the aluminum level was not modified with enhancement of aluminum quantity in intestinal lumen. This pa thway can be similar with calcium transfer through the intestine and is ene rgy dependent because of a decrease of aluminum absorption that follows the removal of glucose and phosphorus.