INTESTINAL-ABSORPTION OF TRACE AMOUNTS OF ALUMINUM IN RATS STUDIED WITH (26)ALUMINIUM AND ACCELERATOR MASS-SPECTROMETRY

1. Until recently studies of intestinal aluminium absorption used phar macological amounts of stable Al-27. 2. To examine the intestinal abso rption of trace amounts of different chemical compounds of aluminium, in the present study we have employed the long half-life isotope of al uminium, Al-26, and accelerator mass spectrometry, Trace amounts of Al -26 (2.7-12.1ng) as the hydroxide, citrate, citrate plus 1 mmol/kg sod ium citrate, or maltolate respectively, were administered to four grou ps of rats (n = 9 per group) by gavage, Blood and urine samples were c ollected for 5h and the Al-26 content (as a percentage of the administ ered dose) determined by accelerator mass spectrometry, 3. The 5h urin ary 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 co nclude that the fractional intestinal absorption of trace oral doses o f aluminium hydroxide is at least 0.1% (compared with the previous est imate of 0.01% using large Al-27 Oral loads), Absorption of aluminium citrate given alone is significantly greater (0.7%) and is further inc reased to 5% by the accompanying sodium citrate, consistent with an en hancing effect of added citrate upon mucosal aluminium permeability. A luminium maltolate absorption approximates that of aluminium hydroxide (0.1%).