[Stabilization of synaptic membranes with alpha-tocopherol against the damaging effect of phospholipases. Possible mechanism of the biological action of vitamin E]

Abstract

Using fluorescent and EPR spin probing techniques, the effects of phospholipases A2, C and D on rat brain synaptosomal membranes were investigated. It was shown that treatment of synaptosomal membranes with phospholipases A2, C and D results in their depolarization and increase of their surface negative charge. In case of phospholipases A2 and C, these changes are also accompanied by a decrease of the microviscosity of the synaptosomal membrane lipid bilayer. alpha-Tocopherol protects synaptosomal membranes against the damaging action of phospholipases. The stabilization of synaptosomes by vitamin E consists in the reconstitution of the transmembrane potential and in an increased microviscosity of phospholipase-treated membranes. The stabilizing effect of alpha-tocopherol is due to the binding of phospholipid hydrolysis products rather than to the inhibition of phospholipases. The observed stabilization of synaptosomal membranes by alpha-tocopherol is interpreted as a feasible mechanism of biological effects of vitamin E on biological membranes.