CI-ATPase and Na+/K(+)-ATPase activities in Alzheimer's disease brains.

The enzyme activities and the protein levels of Cl(-)-ATPase and Na+/K(+)-ATPase were examined in Alzheimer's disease (AD) brains. Cl(-)-ATPase and Na+/K(+)-ATPase activities in AD brains (n = 13) were significantly lower than those in age-matched control brains (n = 12). In contrast, there was no significant difference in anion-insensitive Mg2(+)-ATPase activity between the two groups. Western blot analysis revealed that the protein levels of Cl(-)-ATPase, Na+/K(+)-ATPase and neuron specific Na+/K(+)-ATPase alpha3 isoform were also significantly reduced in AD brains, while the amount of protein disulfide isomerase, one of the house keeping membrane proteins, was not different between the two groups. The data first demonstrated that Cl(-)-ATPase and Na+/K(+)-ATPase are selectively impaired in AD brains, which may reduce the gradients of Na(+), K(+) and Cl(-) across the cell membranes to cause excitotoxic cellular response and the resulting neuronal death.