Rat hindlimb unloading: soleus histochemistry, ultrastructure, and electromyography

• DOI: 10.1152/jappl.1990.69.1.58
• Publication Date: 2017-12-21T13:45:57Z
• Authors: D. A. Riley; G. R. Slocum; J. L. Bain; F. R. Sedlak; T. E. Sowa; J. W. Mellender
• Keywords: Hindlimb; Tonic (physiology); Myofibril; Muscle Atrophy; Fiber type

Soleus muscle atrophy was induced by hindlimb unloading of male Sprague-Dawley rats (305 +/- 15 g) for 4, 7, and 10-14 days. Controls (291 14 were housed in vivarium cages. electromyogram (EMG) activity recorded before during tail suspension. Unloading caused progressive reduction the muscle-to-body weight ratio. After days, type I IIa fibers decreased area 63 47%, respectively. Subsarcolemmal mitochondria myofibrils degraded more rapidly than intermyofibrillar cell membrane. 10 3% exhibited segmental necrosis; affected all high-oxidative fibers. This suggested ischemic injury. By 13 30% possessed central corelike lesions involving primarily Video monitoring revealed abnormal plantar flexion hindfeet 4 days; this posture shortened soleus working range. Corelike indicated adaptation to length. No morphological signs denervation detected. EMG shifted from tonic phasic, aggregate 13% normal after 7 These findings indicate that pathological changes result unloaded contractions, reduced use, compromised blood flow,