Zhongguo ying yong sheng li xue za zhi = Zhongguo yingyong shenglixue zazhi = Chinese journal of applied physiology
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Zhongguo Ying Yong Sheng Li Xue Za Zhi · Nov 2013
Tetanic contraction induces enhancement of fatigability and sarcomeric damage in atrophic skeletal muscle and its underlying molecular mechanisms.
Muscle unloading due to long-term exposure of weightlessness or simulated weightlessness causes atrophy, loss of functional capacity, impaired locomotor coordination, and decreased resistance to fatigue in the antigravity muscles of the lower limbs. Besides reducing astronauts' mobility in space and on returning to a gravity environment, the molecular mechanisms for the adaptation of skeletal muscle to unloading also play an important medical role in conditions such as disuse and paralysis. The tail-suspended rat model was used to simulate the effects of weightlessness on skeletal muscles and to induce muscle unloading in the rat hindlimb. ⋯ Therefore, passive stretch restored normal appearance of Z-disc and resisted in part atrophy of unloaded soleus muscles. The above results indicate that enhanced fatigability of high-frequency tetanic contraction is associated to the alteration in K+ channel characteristics, and elevated SERCA activity and slow to fast transition of myosin heavy chain (MHC) isoforms increases fatigability of intermittent tetanic contraction in atrophic soleus muscle. The sarcomeric damage induced by tetanic contraction can be retarded by stretch in atrophic soleus muscles.