Effect of oral aluminium citrate on short-term tissue distribution of aluminium

Aluminium (Al) concentrations in the plasma, bone, lung, liver, kidney, spleen, duodenum and brain of rats were measured 2, 4 and 24 hr after a single oral dose of 0.46 mmol as Al citrate (1:5 molar ratio). Compared with control animals, very high concentrations were found at 2 hr post-administration in plasma (539 micrograms/litre) and in all tissues except the brain where Al did not change throughout the 24-hr period. The increased levels in the liver (161 ng/g) and lung (89.7 ng/g) at 2 hr were maintained until 4 hr and then decreased. At 24 hr the plasma value decreased to 24.6 micrograms/litre as compared with the peak value of 539 micrograms/litre. In a typical soft tissue such as the kidney the peak at 2 hr of 682 ng/g decreased to 241 ng/g, which was still more than 10-fold greater than the control level. Uniquely, in the case of bone Al increased throughout the period of the experiment. Our results indicate that Al in the citrate form is readily absorbed and that it appears to equilibrate rapidly between plasma and the intracellular compartments of most soft tissues but does not readily permeate the blood-brain barrier. In a group of rats previously given silicic acid in the drinking water and co-administered with the Al dose, the tissue Al distribution pattern at 4 hr post-administration was modified in comparison with the test animals not loaded with silicic acid. Al concentrations in plasma and soft tissues were significantly reduced except for the spleen, in which Al increased, and there was complete inhibition of the very high Al uptake/deposition in bone.