Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/1998
Publication Date: N/A
Citation: Interpretive Summary: Histochemical procedures have been developed and used to differentiate and identify individual skeletal muscle fiber types. It is widely recognized that the major contractile protein (myosin) in skeletal muscle exists in different isoforms (slow to fast electrophoretic migrating mobility). Since histochemical procedures are based on both the metabolic and functional capacity of the muscle, this study was designed to determine whether electrophoretic identification of isoforms of myosin provide similar results in quantification of skeletal muscle as histochemical procedures. Correlation analyses revealed a strong relation between slow-twitch oxidative fibers and slow isomyosin as well as between fast-twitch glycolytic fibers and fast isomyosin. Despite some incompatibility between the different methods investigated, both histochemical as well as electrophoretic analyses yield important information regarding compositional profile of slow and fast skeletal muscle.
Technical Abstract: Highly sensitive enzyme assays developed to differentiate skeletal muscle fibers allow the recognition of three main fiber types namely slow-twitch oxidative (SO), fast-twitch oxidative glycolytic (FOG), fast-twitch glycolytic (FG). Myosin, the predominant contractile protein in mammalian skeletal muscle can be separated based on the electrophoretical mobility under non-dissociating conditions into five isoforms or under dissociating conditions into four myosin heavy chain (MHC) forms. The purpose of the present study was to determine whether the histochemical method of differentiation of fiber types provides results consistent with the electrophoretically identified isomyosin and MHC forms. These comparisons were made using serratus ventralis (SV), gluteus medius (GM) and longissimus muscles (LM) from 13 pigs. Correlation analyses revealed in all muscles a strong relation between SO fibers, the slow isomyosin and MHCI form as well as between the FG fibers, the fast isomyosin and MHCIIx/b content (P<.05). There were no correlations between FOG fiber population and the intermediate isoform. The present study shows that histochemical as well as electrophoretic analyses yield important information about the composition of porcine skeletal muscle and the combination of the two methods may be essential to accurately characterize porcine skeletal muscles.