Stabilization of synaptic membranes by alpha-tocopherol against the damaging action of phospholipases. Possible mechanism of biological action of vitamin E.

Using fluorescent and ESR-spin probes, the effects of phospholipases A2, C and D on rat brain synaptosomal membranes were investigated. It was shown that the exposure of synaptosomal membranes to phospholipases A2, C and D results in their depolarization and an increase of the negative surface potential. In the case of phospholipases A2 and C, these changes are associated with a decrease of the microviscosity of the membrane lipid bilayer. alpha-Tocopherol stabilizes synaptosomal membranes against the damaging action of the phospholipases. This stabilization consists in the reconstitution of the transmembrane potential and an increase of microviscosity of the phospholipase-treated membranes. The stabilizing effect of alpha-tocopherol is due to the binding of phospholipid hydrolysis products, but not to the inhibition of phospholipases. The observed stabilization of synaptosomal membranes by alpha-tocopherol is regarded as a possible mechanism of biological action of vitamin E on biomembranes.