Review

In the normal metabolism of the aerobic cell, oxygen is used for various biochemical reactions. Because of its two lone electrons of parallel spins, the molecular oxygen is stable. However, oxyg n generates Reactive Oxygenated Species or ROS by successive transfer of electrons. The ROS have a strong reactivity and can potentially interact with all other cellular components (lipids, proteins, DNA). They are at the origin of oxidations in chain by creating radicals. The cell has antioxidant systems which limit the effects of the ROS. These systems are composed of enzymes such as glutathione reductase, glutathione peroxidase, etc., and molecules of nonenzymatic nature like the reduced glutathione or vitamins. The production and the destruction of the radicals of oxygen coexist in a weak balance. If this balance is broken in favour of the ROS, an oxidative stress is generated. Xenobiotics could influence this balance by catalysing production of ROS