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KMID : 0811720060100000342
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Korean Journal of Physiology & Pharmacology
2006 Volume.10 No. 0 p.342 ~ p.0
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SINGLE SOLEUS MUSCLE FIBER FUNCTION AFTER HINDLIMB IMMOBILIZATION IN RATS
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Udaka Jun
Ohmori Shintaro
Ishiwata Shin ichi
Iwao Ohtsuki
Kurihara Satoshi
Fukuda Norio
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Abstract
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Disuse atrophy of skeletal muscle results in a marked depression of active force; however, the mechanisms are not fully understood at the molecular level. In the current study, we investigated how hindlimb immobilization affected the contractile function of single skinned soleus fibers from the rat. The left leg was immobilized for six weeks with casting tape to keep the ankle joint in a fully extended position. Immobilization resulted in reduced wet weight of soleus muscle, and the area of single skinned fibers was less in immobilized muscle than in control muscle. We found that in immobilized fibers, maximal Ca2+-actiavated force was reduced and the force-pCa curve was shifted to the lower pCa (higher Ca2+ concentration) side (sarcomere length set at 2.40μm). In order to investigate whether or not the reduction in Ca2+ sensitivity is due to possible isoform switches of troponin molecules, we reconstituted thin filaments of control and immobilized fibers with the identical troponin complex (taken from rabbit psoas muscle). It was found that Ca2+ sensitivity was still lower in immobilized fibers after troponin reconstitution, suggesting that troponin isoform switches, if at all, can not account for functional changes of immobilized fibers. These results favor the interpretation that cross-bridge recruitment is suppressed after immobilization, resulting in active force reductions.
Source: Korean J Physiol Pharmacol.2006 Oct;10(Suppl II):247
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KEYWORD
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Skeletal muscle, atrophy, Ca2+ sensitivity
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