Mechanisms of protection against the damage produced in biological systems by oxygen-derived radicals.

This paper will concentrate on the damage to liver endoplasmic reticulum and plasma membrane fractions that results from exposure to O2- derived radicals and lipid peroxidation. Lipid peroxidation in rat liver endoplasmic reticulum can be produced in various ways involving electron flow out of the NADPH-cytochrome P450 electron-transport chain; analogous reactions occur also in liver plasma membrane suspensions. The subsequent damaging reactions of oxygen-derived radicals and of lipid peroxidation on biological components can be attenuated by various free-radical scavengers and a survey of more than 50 such scavengers in four different systems involving lipid peroxidation has been made. The conditions required for such scavenging reactions to be effective will be outlined, and the difficulties inherent in using such scavengers in vivo will be discussed.