Protection of respiratory chain enzymes from ischaemic damage in adult rat brain slices.

The effect of aglycaemic hypoxia (AH) on the activity of the mitochondrial respiratory chain complexes was measured in superfused adult cortical brain slices. After 15 min of AH the activity of complex II-III was significantly reduced (by 45%) with no change in complex I or IV. Following 30 min of reperfusion the activities of complex II-III and IV were significantly reduced (by 45% and 20% respectively). These reductions in enzyme activity were abolished by removing the external calcium or by the addition of N omega-nitro-L-arginine (LNNA) or an analogue of superoxide dismutase (SOD) manganese [III] tetrakis 4-benzoic acid porphyrin (Mn-TBAP). These data suggest that a reactive oxygen species (ROS) such as peroxynitrite is involved in the reduction of mitochondrial complex activities following AH.