Exp Neurobiol 2:25-32, 1993

The Changes of the Skeletal Muscle Fiber Type after Cross Innervation in the Rat by Immunohistochemical Study.

Jong Eun Lee, You Sun Kang, Won Taek Lee, Seung Jin Lee, Kyung Ah Park

Department of Anatomy, Yonsei University College of Medicine, Seoul 120-749, Korea

The skeletal muscle of the mammals consists of various types of muscle fibers in the same muscle. Muscle fibers could be classified according to the enzyme activity in the mitochondria, ATPase activity of myosin and contraction velocity. The purpose of the study is the usefulness of the immunohistochemical method to classify muscle fiber types.

In this study, immunohistochemical stain has been done using antibodies to fast-myosin and parvalbumin in normal state and after cross innervation. Using immunohistochemical stain of fast-myosin, muscle fiber type could be classified as follows; type 1 for the weakest and type 2 for the intermediate and type 3 for the strongest reaction. The extensor digitorum longus (EDL) consists of 5.6 % of type 1 and 94.4 % of type 3, while soleus muscle consists of 95.1 % of type 1 and 4.9 % of type 3 and. After cross innervation, type 3 muscle fiber decreased enormously and type 2 and 1 increased in EDL muscle, while type 3 and 2 increased in soleus muscle.

Immunohistochemical study upon parvalbumin showed similar results as fast myosin. After immunostaining upon parvalbumin, and three types were classified in EDL and soleus muscle: the strongest reactivity (type III), the weakest reactivity (type I) and intermediate type (type II) . In EDL muscle, type III was 67.8 % and this type III was decreased and type I was increased after cross innervation.

From the above results, it could be concluded that immunostaining upon fast-myosin and parvalbumin is one of the better ways of identifing muscle fiber type, and it would be helpful to study the immunoreactivity upon fast-myosin and parvalbumin to investigate the muscle innervation.

Key Words: rat, cross innervation, immunohistochemical study, fast-myosin, parvalbumin