The continuum of pure and hybrid myosin heavy chain-based fibre types in rat skeletal muscle.
The myosin heavy chain (MHC)-based fibre composition of adult rat adductor magnus (AM) and tibialis anterior (TA) muscles was investigated using single fibre analysis. Microelectrophoresis performed on single fibre fragments demonstrated a predominance of pure fast MHC-based fibre types (expressing only one fast MHC). Most of the fibres analysed from both the AM (72%) and TA (50%) were pure type IIB (expressing only MHCIId). Pure type IID fibres (expressing only MHCIId) were also abundant in AM (20%) and TA (18%). In addition, hybrid fibres coexpressing MHCIIb and MHCIId in varying proportions (fibre types IIBD and IIDB) were found, as well as fibres coexpressing MHCIId and MHCIIa with a predominance of MHCIId (type IIDA) and some C fibres (coexpressing MHCI and MHCIIa in varying proportions). Considered altogether, these data reflect the dynamic nature of adult skeletal muscle fibres and indicate a continuum of MHC-based fibre types in normal rat muscle with transitions in the order IIB<==>IIBD<==>IIDB<==>IID<==>IIDA<==>IIAD<==>II A<==>IIC<==>IC<==>I.
Staron
R S
RS
Faculty of Biology, University of Konstanz, Germany.
Pette
D
D
D000818:Animals; D006614:Hindlimb / Q000378:metabolism; D006651:Histocytochemistry; D009119:Muscle Contraction / Q000502:physiology; D009132:Muscles / Q000166:cytology / Q000294:innervation / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D009412:Nerve Fibers / Q000378:metabolism; D051381:Rats
D009218:Myosins