Experimental investigations on the hypokinesis of skeletal muscles with different functions, VIII. Effect of plaster-cast immobilization on the contractile properties of rat skeletal muscles with different functions.

The plaster-cast immobilization of the right hind limbs of rats has been investigated. Examinations were performed on the changes in weight of both types of skeletal muscles, i.e. the fast and the slow ones, the m. extensor digitorum longus and the m. gastrocnemius on the one hand, and the m. soleus on the other. The most significant loss in weight was observed in the gastrocnemius muscle. The ATP-Ca2+-induced isometric tension as well as the speed of contraction of glycerine-treated myofibrillar preparations considerably decreased as a result of 28-day immobilization. The most marked change was observed in the soleus muscle. There was a similar decrease in the specific activity of myofibrillar myosin ATPase prepared from immobilized muscles. The specific activity of K+-EDTA myosin ATPase did not change.