Oxidants and antioxidative defense.

The role of oxygen free radicals and other oxidants in several diseases has been well established over the past decade. Whereas it was long known that high doses of oxidants may damage or kill cells, the effect of low doses or long-time exposure to small flux rates of oxidants have been the focus of the free radical research until now. Here one has to take into account that most physiological and pathophysiological actions of oxidants and free radicals are based on the permanent action of small doses and flux rates. This includes effects of oxidants on signal transduction pathways and gene expression patterns. Therefore, only a few answers can be given today on the relevance of the effects of low doses of oxidants.