The influence of citrate, maltolate and fluoride on the gastrointestinal absorption of aluminum at a drinking water-relevant concentration: A 26Al and 14C study

The objectives were to test the null hypotheses that (1) citrate, maltolate, and fluoride do not significantly influence oral Al bioavailability, Cmax or Tmax at an Al dose relevant to drinking water exposure; and (2) Al citrate and maltolate are absorbed intact from the gastrointestinal tract. Male Fisher rats were given 1 ml of solution intra-gastrically containing 1 nCi 26Al (65 nmol total Al) as the Al3+ ion, or as complexes with 14C-citrate, 14C-maltolate or fluoride, during concurrent 27Al iv infusion. Blood was repeatedly collected for serum 26Al, total Al and 14C quantification. Absorption parameters were estimated using WinNonlin. Al bioavailability, Cmax and Tmax from the ion, citrate, maltolate, and fluoride were 0.29 ± 0.11%, 0.61 ± 0.31%, 0.50 ± 0.25%, and 0.35 ± 0.10%; 659 ± 195, 1073 ± 250, 881 ± 356, and 880 ± 295 fg/ml; and 1.2 ± 0.9, 1.0 ± 1.1, 1.3 ± 1.0, and 1.0 ± 0.9 h (X ± SD) respectively. Serum 14C was ∼100 times higher than 26Al. The results suggest a non-significant enhancement of oral Al bioavailability by citrate and maltolate, some Al complex dissociation in the GI tract, and less absorption of Al than citrate or maltolate. The presence of citrate, maltolate and fluoride, at a similar molar concentration to Al, would not be expected to greatly influence Al absorption from drinking water.