The membrane effects of vitamin E, cholesterol and their acetates on peroxidative susceptibility.

Ox-brain phospholipid liposomes provide an organised membrane structure as well as a substrate for lipid peroxidation. Vitamin E is a poor antioxidant outside the membrane but has considerable activity within. Inclusion of its acetate derivative confirmed the dual role of vitamin E as both a stabilising structural component and free-radical scavenger. Cholesterol similarly stabilises the membrane but does not appear to significantly protect by radical scavenging. Its functions are closely related to the amount and type of phospholipid present in the membrane. Changes in oxidative susceptibility following free-radical stress provide a sensitive measure of membrane structural organisation.