Free radical toxicology and antioxidant defence.

1. A large number of compounds that have toxic effects can be metabolized to free radicals and secondary reactive oxygen species. These may be directly damaging or may affect cell function by altering regulatory mechanisms through changing redox status. 2. Protection is provided by an integrated system of antioxidant defences. This includes reduced glutathione, one of the functions of which is to scavenge free radicals. It acts by channelling radicals to superoxide so that the one enzyme, superoxide dismutase, has a major control over radical reactions in the cell.