Effect of long-term aluminum feeding on kinetics attributes of tissue cholinesterases

Aluminum (Al) is considered a potential etiological factor in Alzheimer's disease (AD). Neurotoxicity from excess brain exposure to Al is documented from both clinical observations and animal experiments. A key role of the acetylcholine system in memory disturbances that characterize AD has been reported. On this basis, we studied the effect of long-term Al feeding on kinetic properties of cholinesterases employing the rat as experimental model. Animals were given prolonged treatment with soluble salts of Al (100 mg AlCl3/kg body weight mixed with food for 100-115 days), and the kinetic properties of cholinesterases (acetylcholinesterase, AChE, and butyrylcholinesterase, BChE) were determined in different tissues. Prolonged treatment with Al had no effect on the Km values of the soluble and membrane-bound forms of AChE in the brain, but V-max was instead decreased in all the components of soluble and membrane-bound forms of AChE in the brain. In addition, the Al treatment resulted in complete loss of the component II of erythrocyte membrane AChE. Surprisingly, after prolonged treatment with Al, higher V-max was observed in all the components of soluble and membrane-bound forms of BChE in the heart and liver. Variable effects of All exposure were observed on temperature kinetic properties of cholinesterases. Altogether these findings indicate that long-term All feeding results in inhibition of AChE, while an opposite effect is observed on BChE. Decreased V-max of the brain AChE could represent the mode of action through which Al may contribute to pathological processes in Al-induced neurotoxicity. (C) 2002 Elsevier Science Inc. All rights reserved.