We review evidence implicating mitochondrial dysfunction in the pathog
enesis of ischaemia/reperfusion injury. The lesion has been identified
as a non selective pore that is triggered by Ca2+ and particular meta
bolic derangements associated with this form of injury, namely falling
ATP, raised P(i) and oxidative stress. Once activated, the pore flick
ers between open and closed states and disrupts mitochondrial energy t
ransduction, allowing ATP hydrolysis by the F(I)F(o) ATPase. Pore acti
vation is prevented by cyclosporin A, which also retards the onset of
necrosis in heart cells subjected to substrate-free anoxia and allows
partial regeneration of ATP on reoyxgenation.