EFFECT OF REPERFUSION FOLLOWING CEREBRAL-ISCHEMIA ON THE ACTIVITY OF THE MITOCHONDRIAL RESPIRATORY-CHAIN IN THE GERBIL BRAIN

The effect of reperfusion following 30 min of cerebral ischaemia on br ain mitochondrial respiratory chain activity has been studied in the g erbil. The state 3 respiration rates with both FAD- and NAD-linked sub strates were reduced after ischaemia. After 5 min of reperfusion, stat e 3 respiration with FAD-linked substrates was restored, but levels of NAD-linked substrates did not return to control values until 30 min o f reperfusion. By 120 min of reperfusion state 3 respiration decreased relative to control values with all substrates studied. Measurement o f the individual respiratory chain complexes showed that complex I, co mplex II-III, and complex V activities were reduced after ischaemia. B y 5 min of reperfusion complex II-III activity was restored, but the a ctivities of complexes I and V did not return to control Values until 30 min of reperfusion, In contrast, complex IV activity was unaffected by ischaemia or 5 and 30 min of reperfusion but was significantly red uced after 120 min of reperfusion, possibly owing to free radical prod uction and lipid peroxidation.