期刊
NEUROBIOLOGY OF DISEASE
卷 18, 期 2, 页码 356-365出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.nbd.2004.09.016
关键词
skeletal muscle; resting chloride conductance; chloride channel; myosin heavy chain; excitation-contraction coupling; atrophy; disuse; simulated microgravity; hindlimb unloading
The hindlimb unloading (HU) rat is a model of muscle disuse characterized by atrophy and slow-to-fast phenotype transition of the postural muscles, such as the soleus. We previously found that the resting sarcolemmal chloride conductance (gCl) that is typically lower in slow-twitch myofibers than in fast ones increased in soleus fibers following I to 3 weeks of HU in accord with the slow-to-fast transition of myosin heavy chain (MRC) isoforms. Nevertheless, the gCl already raised after a 3-day HU, whereas no change in MHC expression was detected. The present work evaluates the ability of soleus muscle to recover on return to normal load after a short (3 days) or long (2 weeks) disuse period. The changes observed after a 2-week HU were slowly reversible, since 3-4 weeks of reloading were needed to completely recover gCl, fiber diameter, MHC expression pattern, as well as the mechanical threshold Rheobase, an index of calcium homeostasis. After 3-day HU, the gCl increased homogeneously in most of the soleus muscle fibers and gCl recovery was rapidly completed after 4-day reloading. These results suggest different induction mechanisms for gCl augmentation after the short and long HU periods, as well as a possible role for gCl in the slow muscle adaptation to disuse. (C) 2004 Elsevier Inc. All rights reserved.
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