Suppression of ischemia-reperfusion injury by liposomal superoxide dismutase in rats subjected to tourniquet shock.
To investigate the role of oxygen-derived free radicals in the pathogenesis of tourniquet shock, the authors present an experimental animal model. Two groups of rats were fastened with rubber tubes on both thighs (1.5 kg/cm2) for 6 h under pentobarbital anaesthesia. One group was administered liposomal superoxide dismutase (L-SOD 30,000 U/kg body weight), and the other liposome as a control 3 h prior to tourniquet removal. No rats in the control group (n = 20) survived more than 24 h after reperfusion, whereas 55% of animals treated with L-SOD (n = 20) survived for 24 h or more, and two recovered completely (P less than 0.005). Blood samples were obtained from the abdominal aorta after laparotomy of anaesthetized rats of both groups at different time intervals. Changes in the hematocrit value and blood urea nitrogen during the early periods after reperfusion were attenuated by prior administration of L-SOD, and the total plasma SOD activity of the control animals decreased promptly and continuously throughout the experimental period. This experimental model was very useful to study the pathogenesis of tourniquet shock with respect to reproducibility, induction of the shock stages and mortality. It is thought that oxygen-free radicals are involved in the induction of tourniquet shock, and L-SOD was, to a certain extent, effective against reperfusion injury in the early stages of shock.