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Effects of inactivity on myosin heavy chain composition and size of rat soleus fibers
Author(s) -
Grossman Elena J.,
Roy Roland R.,
Talmadge Robert J.,
Zhong Hui,
Edgerton V. Reggie
Publication year - 1998
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(199803)21:3<375::aid-mus12>3.0.co;2-z
Subject(s) - myosin , medicine , endocrinology , soleus muscle , atrophy , chemistry , major histocompatibility complex , biology , skeletal muscle , biochemistry , gene
Myosin heavy chain (MHC) and fiber size properties of the adult rat soleus were determined after 4–60 days of complete inactivity, i.e., lumbar spinal cord isolation. Soleus atrophy was rapid and progressive, i.e., 25% and 64% decrease in weight and 33% and 75% decrease in fiber size after 4 and 60 days of inactivity, respectively. Changes in MHC occurred at a slower rate than the atrophic response. After 15 days there was de novo expression of type IIx MHC (∼10%). By 60 days, type IIx MHC accounted for 33% of the total MHC content, and 7% of the fibers contained only type IIx MHC. The relative amount of type I MHC was reduced from 93% in control to 49% after 60 days of inactivity. Therefore, the effects of 60 days of inactivity suggest that during this time period at least 75% of fiber size and ∼40% of type I MHC composition of the adult rat soleus can be attributed to activation‐related events. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:375–389, 1998.