OXYGEN IS necessary for cell life. Ironically, it may also be responsible for cell death.
Whenever a disease or injury deprives a tissue of oxygen, reestablishing blood flow and therefore reintroducing oxygen may damage the tissue further. Some researchers hypothesize that oxygen free radicals play a major role in this process.
Investigators have looked at the role of free radicals in reperfusion injury of the heart, intestine, pancreas, and lung (JAMA 1984;251:2187, 2191-2192), but more recently they have also attempted to link free radicals to ischemia-reperfusion brain injury.
Normally, oxygen is metabolized to two molecules of water through the addition of four electrons that accompany four hydrogen atms. The process occurs in the mitochondria and is controlled by the enzyme cytochrome oxidase.
As each electron is added to an oxygen molecule, highly reactive compounds are produced in the presence of hydrogen ions. One electron produces superoxide anion radical, a second