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Effects of immobilization on rat hind limb muscles under non‐weight‐bearing conditions
Author(s) -
Jaspers Stephen R.,
Fagan Julie M.,
Satarug Soisungwan,
Cook Paul H.,
Tischler Marc E.
Publication year - 1988
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/mus.880110508
Subject(s) - hindlimb , soleus muscle , myofibril , muscle hypertrophy , chemistry , in vitro , sarcoplasm , protein degradation , endocrinology , weight bearing , in vivo , medicine , sarcomere , anatomy , biochemistry , skeletal muscle , myocyte , biology , surgery , endoplasmic reticulum , microbiology and biotechnology
Dorsiflexion of one unloaded hind limb caused hypertrophy of the soleus relative to weight‐bearing controls and faster growth of the plantaris and gastrocnemius muscles relative to the contralateral freely moving muscles. Unloading of the soleus muscle diminished primarily myofibrillar proteins whereas stretching increased all proteins. Stretching the soleus increased RNA, accelerated, especially, in vitro synthesis of sarcoplasmic proteins, and diminished in vitro proteolysis. Both in vivo and in vitro results showed slower synthesis and faster degradation in the freely moving than in the weight‐bearing soleus muscle, faster synthesis and slower degradation in the stretched than in the freely moving soleus muscle, and faster degradation in the stretched than in the weight‐bearing soleus muscle. Hence, stretching of the soleus muscle prevented changes in mass and protein metabolism produced by unloading. Shortening of the extensor digitorum longus muscle produced less muscle growth, slowed in vitro protein synthesis, and lowered RNA relative to the contralateral, freely moving muscle.