Intestinal absorption of trace amounts of aluminium in rats studied with (26)aluminium and accelerator mass spectrometry

1. Until recently studies of intestinal aluminium absorption used pharmacological amounts of stable Al-27. 2. To examine the intestinal absorption of trace amounts of different chemical compounds of aluminium, in the present study we have employed the long half-life isotope of aluminium, Al-26, and accelerator mass spectrometry, Trace amounts of Al-26 (2.7-12.1ng) as the hydroxide, citrate, citrate plus 1 mmol/kg sodium citrate, or maltolate respectively, were administered to four groups of rats (n = 9 per group) by gavage, Blood and urine samples were collected for 5h and the Al-26 content (as a percentage of the administered dose) determined by accelerator mass spectrometry, 3. The 5h urinary Al-26 excretion amounted to 0.1+/-0.02, 0.7+/-0.2, 5.1+/-1.5 and O.1+/-0.1% of administered dose in the four groups respectively, There was a strong positive correlation between peak plasma Al-26 (r = 0.98) and urinary Al-26 excretion in individual animals (P<0.001), 4. We conclude that the fractional intestinal absorption of trace oral doses of aluminium hydroxide is at least 0.1% (compared with the previous estimate of 0.01% using large Al-27 Oral loads), Absorption of aluminium citrate given alone is significantly greater (0.7%) and is further increased to 5% by the accompanying sodium citrate, consistent with an enhancing effect of added citrate upon mucosal aluminium permeability. Aluminium maltolate absorption approximates that of aluminium hydroxide (0.1%).