Superoxide, iron, vascular endothelium and reperfusion injury.

It is proposed that vascular endothelium has an intrinsic capacity to generate O2- for regulatory purposes such as inactivation of endothelium-derived relaxing factor. Ischaemia can disrupt the functioning of this oxidant-generating system, resulting in greater O2- generation when O2 is restored. Ischaemia-induced cellular injury can also lead to release of iron ions, that, upon reperfusion, cause conversion of O2- and H2O2 to powerfully-oxidizing species (such as .OH) that further injure the endothelium.