Effect of aluminum on rat brain. Enhancement by calcium deficiency.

Experimental aluminum intoxication was performed in rats both with normal diet and calcium-deficient diet feeding for 4 weeks in order to elucidate the neurotoxic effect of aluminum and the relationship between aluminum and calcium metabolism. Ultrastructural changes of the cerebrum were studied chronologically. In addition, the distribution of aluminum in the neurons was analyzed using an X-ray microprobe analysis. In the group with aluminum administration alone, the endothelial cells, pericytes, astrocytes and synapses showed only mild degenerative changes. However, no significant abnormality was present in the axons, dendrites and perikaryon of the neurons. No detectable aluminum was present in the neurons. When aluminum intoxication was coupled with calcium deficiency, morphologic changes as seen in the group with aluminum administration alone were observed in the blood vessels, astrocytes and synapses from the early stage. The synaptic degeneration was more prominent. The degenerative changes were also present in the axons, dendrites and even perikaryon. The presence of aluminum was demonstrated in the neurons. These results suggest that in the secondary hyperparathyroidism due to calcium deficiency, aluminum transportation to the neurons is enhanced and aluminum neurotoxicity causes more prominent degeneration.