Effects of hyperbaric oxygen on glucose, lactate, glycerol and anti-oxidant enzymes in the skeletal muscle of rats during ischaemia and reperfusion.

1. Hyperbaric (HBO(2)) and topical oxygen represent two accepted options to oxygenate tissues. The aim of the present study was to investigate the effect of HBO(2) on energy metabolism and anti-oxidant enzymes in a rat model of ischaemia-reperfusion (IR) skeletal muscle injury. 2. In the first study, 16 rats were randomized to a HBO(2)-treated group (Group 1; n = 8) and an untreated group (Group 2; n = 8). Under general anaesthesia, right hind limb ischaemia was produced by application of a rubber-band tourniquet for 3 h. After 2 h ischaemia, Group 1 rats received HBO(2) during the last hour of ischaemia. The HBO(2) consisted of 100% oxygen delivered at 282.8 kPa absolute pressure. Group 2 rats were not treated. Following the ischaemic period, the tourniquet was released for 1 h. A microdialysis probe was used to sample lactate, glucose and glycerol concentrations in the muscle extracellular tissue every 15 min throughout each experiment. 3. In the second study, 24 rats were randomized into four groups (n = 6 each). The first two groups were subjected to the IR injury protocol outlined above and either treated (Group 1) or untreated (Group 2) with HBO(2). Group 3 rats were anaesthetized, did not undergo IR injury, but underwent HBO(2) treatment. Group 4 rats were anaesthetized but did not undergo either IR injury or HBO(2) treatment. At end of each experiment, the biceps femoris muscle was removed and assayed for superoxide dismutase (SOD) and catalase (CAT) activity. Malondialdehyde (MDA) was measured to estimate the extent of membrane lipid peroxidation. 4. Three hours of skeletal muscle ischaemia resulted in a gradual decrease in the glucose concentration and a gradual increase in the lactate concentration within the extracellular fluid of the affected skeletal muscle tissue. Treatment with HBO(2) had no effect on the glucose concentration; however, HBO(2) significantly attenuated the ischaemia-induced increase in lactate and glycerol. In both groups, glucose concentration increased rapidly during reperfusion; glucose concentration returned to pre-ischaemic levels 15 min after reperfusion both with and without HBO(2). 5. Catalase activity and MDA increased significantly after 1 h of reperfusion. The HBO(2) attenuated the reperfusion-induced increase in CAT activity and MDA. 6. The results of the study suggest that HBO(2) may have some beneficial effect by decreasing lactate and glycerol levels and modulating anti-oxidant enzyme activity in postischaemic skeletal muscle in our rat model of tourniquet-induced IR skeletal muscle injury.