Indicators of oxidative injury and alterations of the cell membrane in the skeletal muscle of rats submitted to ischemia and reperfusion

Background, Oxygen free radicals are considered to be important components involved in the physiopathological tissue alterations observed during ischemia and reperfusion, The objective of the present study was to investigate oxidative stress based on indicators of oxygen free radical activity and on the changes in behavior of the lipoprotein membrane (O-phosphoserine) in the skeletal muscle of rats. Material and methods. Twenty Wistar rats were divided into two groups of 10. One group was submitted to 3 h of total ischemia by applying a tourniquet to the hind limb and the contralateral hind limb was used as control. The second group was submitted to the same procedure and was reperfused for 45 min after 3 h of ischemia by removing the tourniquet, where the contralateral hind limb of the same animal was used as control. Muscle biopsies were taken after ischemia and reperfusion and the parameters indicating oxidative stress (reduced and oxidized glutathione, malondialdehyde, glutamine synthetase, protein carbonyl) and O-phosphoserine (OPS) alterations were analyzed. Results. The following results display control versus experimental hindlimbs groups obtained from the same animal. The skeletal muscle of rats submitted to total ischemia of 3 h duration showed increased OPS release (2.69 +/- 4.52 vs 8.03 +/- 7.20; n = 10; P = 0.024) and no change in reduced and oxidized glutathione, glutamine synthetase, protein carbonyl, or malondialdehyde. After 45 min of reperfusion there was an increase in oxidized glutathione levels (0.30 +/- 0.06 vs 0.39 +/- 0,09; n = 8; P = 0.02) and malondialdehyde levels (154.78 +/- 26.13 vs 206.30 +/- 47.30; n = 9; P = 0.008), a fall in glutamine synthetase (21.80 +/- 3.61 vs 13.52 +/- 6.78; n = 9; P = 0.004), and a return of OPS to levels close to the initial ones. No changes in reduced glutathione or protein carbonyl were observed in the two groups studied. Conclusions. After a total ischemia duration of 3 h there were signs of damage to the phospholipid membrane of the rat skeletal muscle, as demonstrated by the elevation of OPS and the few or no oxidative changes in the cell. After 45 min of reperfusion, oxidative damage to the lipoprotein components of the cell membrane was observed, characterized by elevations of oxidized glutathione and malondialdehyde levels and a fall in glutamine synthetase levels, (C) 2000 Academic Press.