DEVELOPMENT OF ISCHEMIC CONTRACTURE IN ISOLATED SKELETAL-MUSCLES - RELATION TO THE CAPACITY FOR ANAEROBIC GLYCOLYSIS

In order to evaluate the dependence of the rate of ischemic contracture development in isolated skeletal muscles on the capacity for anaerobic glycolysis, factors affecting ischemic contracture development were examined using rat soleus and quadriceps muscles. The contracture developed faster in slow-twitch oxidative (SO) fibers than in fast-twitch glycolytic (FG) fibers. In both types of fibers, the rate of contracture development was inversely related to the medium pH. Addition of lactate increased the rate of contracture development. In FG fibers, the lactate level during contracture was directly, and the glycogen level inversely, proportional to the medium pH. An increase in muscle lactate level by 4-h swimming accelerated the contracture development, and reduced further lactate accumulation during contracture. Types of exercise training known to influence the capacity for anaerobic glycolysis (interval training and repeated fast climbing and swimming) decreased the velocity of contracture development. Isoprenaline administration in vivo accelerated contracture development in association with reduced lactate level during contracture. Swimming training counterbalanced the action of isoprenaline. Adrenalectomy accelerated contracture development in SO fibers, and decreased lactate accumulation during contracture in FG fibers. In adrenalectomized rats, the effects of exercise were more pronounced in SO fibers than in FG fibers. These results indicate that the rate of contracture development in isolated skeletal muscle is inversely related to the capacity for anaerobic glycolysis.