A brain soluble fraction inhibits synaptosomal membrane but not astrocyte ATPase activity.

Since a brain soluble fraction (peak II) is known to be able to inhibit synaptosomal membrane Na+, K(+)-ATPase activity, here we attempted to compare its effect on cellular and subcellular brain components such as synaptosomal and astrocytic membranes, as well as mitochondrial preparations. The difference between total and Mg(2+)-ATPase activity was noteworthy in synaptosomal membranes but proved unremarkable in astrocytic and mitochondrial preparations. Peak II highly inhibited total ATPase in synaptosomal membranes but failed to modify enzyme activity in astrocytic and mitochondrial preparations. Findings suggest cellular and subcellular specificity of peak II on brain ATPase activity.