Reduction of cold injury by superoxide dismutase and catalase.

The pathophysiology of cold injury was examined by cooling a hind leg of an anesthetized New Zealand white rabbit. A flow probe and a thermocouple were placed in the leg to be cooled to monitor the blood flow and tissue temperature. After baseline measurements, the leg was cooled with a freezing mixture up to 0 degrees C, which was followed by rewarming. The other leg served as control. In the experimental group, liposome-bound superoxide dismutase and catalase were infused through the femoral vein 15 minutes prior to putting the freezing mixture on the leg. Salicylic acid was injected through the femoral vein at the end of some experiments to assay hydroxy radical (OH). Our results demonstrated reduction of local blood flow in cold-exposed leg, indicating development of ischemia. Creatine kinase and lactage dehydrogenase were increased during rewarming in conjunction with hydroxyl radical formation, phospholipid breakdown, and lipid peroxidation. Treatment with superoxide dismutase and catalase reduced OH formation, prevented phospholipid degradation, and decreased creatine kinase, lactate dehydrogenase, and malonaldehyde formation. These results indicate that rewarming of cooled tissue is associated with "rewarming injury" similar to "reperfusion injury", and that oxygen-derived free radicals play a significant role in the pathophysiology of such injury.