CYTOCHROME-C OXIDASE AND CARDIOLIPIN ALTERATIONS IN RESPONSE TO SKELETAL-MUSCLE ISCHEMIA AND REPERFUSION

The effect of 2 and 4 h of tourniquet ischaemia followed by 1 h of reperfusion on the major mitochondrial phospholipids and on the cytochrome c oxidase kinetic parameters has been investigated in rat skeletal muscle. There was no change either in the mitochondrial phospholipid conent or in the V(max) and the K(m) of the enzyme after a 2 h of ischaemia with and without subsequent reprefusion. Four hours of ischaemia had no effect on the lecithin and the cephalin content, while the cardiolipin content decreased as well as the V(max) of the enzyme (P < 0.05). Tissue reperfusion caused a dramatic decrease in both cardiolipin (55% of the control, P < 0.01) and V(max) (38% of the control, P < 0.01). The corresponding reduction in lecithin and cephalin contents was 12% and 14% respectively (P < 0.05). The K(m) remained unchanged at all conditions. These findings suggest that mitochondrial dysfunction in response to ischaemia and reperfusion could be a consequence of the reperfusion itself following severe ischaemia. The results are discussed in terms of cardiolipin peroxidation and cytochrome oxidase as a functional parameter.