Abstract
Purpose: Dystrophin-glycoprotein complex (DGC) and focal adhesion complex (FAC) are transmembrane structures of muscle fibers which make a linkage between extracellular matrix (ECM) and intracellular cytoskeleton. They play a role of transmitting force from myofibrils to outside the fibers, but it is unknown how DGC and FAC are associated with contractile properties of skeletal muscles. The purpose of this study was to investigate whether the expression of dystrophin (component of DGC) and β1 integrin (component of FAC) have muscle type specificity in rat skeletal muscle. Methods: Soleus (SOL), plantaris (PLA), extensor digitorum (EDL), tibialis anterior (TA) muscles were dissected from male Wistar rats. The content of dystrophin and β1 integrin and the composition of myosin heavy chain isoforms were measured in these muscles. Immunohistochemical staining for dystrophin and β1 integrin in the cross-section of these muscles was also performed. Results: The dystrophin relative content was different among the muscles (SOL < PLA < EDL < TA), and β1 integrin was less contained in TA than in the other muscles. β1 integrin was expressed more strongly in type I and type IIa fibers than in type IIx and IIb, whereas dystrophin did not show fiber type specific expression. Discussion: Our data suggest that the expression of both DGC and FAC are contained more abundantly in the muscles which are recruited more frequently, increasing the efficiency of transmitting contractile force during daily physical activity. [J Physiol Sci. 2007;57 Suppl:S92]
