An age‐related type IIB to IIX myosin heavy chain switching in rat skeletal muscle

• DOI: 10.1111/j.1748-1716.1993.tb09493.x
• Publication Date: 2008-12-10T14:49:07Z
• Authors: L. LARSSON; D. BIRAL; M. CAMPIONE; S. SCHIAFFINO
• Keywords: Motor unit; Tibialis anterior muscle; Myofibril

A novel fast‐twitch motor unit type, called the IIX‐myosin heavy chain (MHC) unit, identified by glycogen depletion technique together with a series of monoclonal antibodies (mAbs) specific for MHCs, has been isolated recently in rat tibialis anterior muscle. In young animals, this physiological, biochemical and morphometrical properties which separate it from IIA‐ IIB‐MHC units. old age, on other hand, IIX‐MHC units display resembling Based these results was proposed that transition IIB to IIX occurs during ageing. an attempt clarify point, MHC composition 6% SDS‐PAGE immunoblotting analysis, using mAbs antibodies, same muscles (3–6 months, n = 9) (20–24 16) rats single had previously. The comigrates HA‐MHC band only two bands are observed muscle, i.e. IIA‐IIX‐and bands. significant increase ( P < 0.001) average relative amount HA‐IIX —MHC (45 ± 17%) as compared (23 4%) accompanied corresponding decrease content. It demonstrated analysis trace amounts IIA‐MHC were detectable IIA‐IIX‐MHC both TA muscles, indicating substantial content age. Thus, present previous observations at level strongly support age‐related type IIB‐ IIX‐MHC.