DISTRIBUTION AND MORPHOLOGY OF SKELETAL-MUSCLE LESIONS AFTER EXPERIMENTAL RESTRAINT STRESS IN NORMAL AND STRESS-SUSCEPTIBLE PIGS

Six normal and 22 stress-susceptible (SS) pigs were subjected to exper imental restraint stress to test the hypothesis that SS pigs are more affected by stress-induced skeletal muscle lesions than normal pigs. T he stress was provoked by a 12 min intravenous infusion of the myorela xant succinylcholine at a dose which induced leg paralysis. At necrops y 2-3 days after the stress, 24 muscles were examined macro- and micro scopically. The plasma levels of noradrenaline and adrenaline increase d significantly during the stress, especially in SS pigs. Significantl y higher scores of acute muscle lesions (degeneration and phagocytosis ) were recorded in the SS pigs than in the normal pigs. The antebrachi al flexor muscles, m. gastrocnemius, crural flexor muscles, m. serratu s and m. intercostalis were most affected, while m. semitendinosus, m. masseter, crural extensor muscles, m. quadriceps and antebrachial ext ensor muscles were the least affected. The muscle regeneration of SS p igs was greater than that of normal pigs indicating more active rhabdo myolysis in SS pigs than in normal pigs. The muscle lesions were also reflected in increased serum levels of creatine kinase(CK), aspartate aminotransferase (ASAT), potassium and creatinine in SS pigs. It is co ncluded that the restraint stress induced skeletal muscle lesions and increased sympathetic activity, predominantly in SS pigs. It was also shown that certain skeletal muscles are more affected by rhabdomyolysi s than others.