Gastrointestinal absorption of aluminum in rats using 26Al and accelerator mass spectrometry.

Using the technique of Accelerator Mass Spectrometry (AMS), 26Al has been measured in plasma, liver, urine and bone of normal rats at 8, 24 and 48 hours after ingestion of trace amounts of Al (3.8 ng of 26Al and 63 ng of stable 27Al), both in citrate-free and citrate-containing solutions. Our data show that under physiological conditions, namely at normal levels of dietary intake, intestinal Al absorption is approximately 0.04%, and is not significantly enhanced by the presence of citrate. Interestingly, the amount of Al retained by bone (0.02%) is comparable to that excreted in urine during 48 h (0.02%). Our estimate of gastrointestinal absorption is more than two orders of magnitude smaller than that estimated by Day et al. [1991], also using 26Al, for a single human subject.