Muscle types ; NADH-TR stain ; ATPase stain ; Immunohistochemical stain upon fast myosin ; Rat skeletal muscle
Abstract
The skeletal muscle of mammals consists of various types of muscle fibers. Muscle fibers could be classified according to the enzyme activity in the mitochondria, ie, nicotinamide dinucleotlde-tetyazolium reductase (NADH-TR), ATPase activity of myosin and contraction velocity. The purpose of this study is to compare the muscle fiber types using immunohistochemical staining and enzyme histochemical stainings. Muscle fiber types could be classified in the ear1iest period using the immunohistochemical stain of fast myosin. The immunoreactivity of fast myosin showed strong reactions in the extensor digitorum longus and soleus muscle on the 1st day after birth. Muscle fiber types could be identified first on the 5th day after birth using the ATPase stain and the 20th day using the NADH-TR stain. In the extensor digitorum longus muscle, the adult pattern of the muscle fiber type appealed on the 5th day after birth in the ATPase stain and immunohistochemical stain of fast myosin, while they were not shown on the 20th day after birth in the NADH-TR stain. In the soleus muscle, the adult pattern appeared on the 14th day after birth in the ATPase stain but they were not shown on the 20th day after birth in the NADH-TR stain. In contrast to the adult pattern, the intermediate type 2 fibers could be observed until the 10th day after birth. From the above results, We believe that the immunostain upon fast myosin is the fastest and most efficient way of identifing muscle fiber type.