Immunohistochemical classification of skeletal muscle fibers

Mammalian skeletal muscle fibers have several types of myosin heavy chain (MHC) isoforms. Immunohistochemical techniques enable us to identify the MHC isoform type in a single muscle fiber, i.e., MHCI, MHCIIa, MHCIIx, or MHCIIb. In addition, hybrid single fibers having more than one MHC isoform type can be classified using immunohistochemistry. The presence of different MHC isoform(s) in a single fiber correlates with the maximal contractile velocity and the enzyme histochemical reaction of the myofibrillar adenosine triphosphatase. The adaptive response of the skeletal muscle is the basis of the fiber-type transformation depending on the phenotypic expression pattern in several MHC isoforms. In this review article, we address the availability of the monoclonal antibodies which recognize specific MHC isoform(s) in a single fiber.