Tetanic contractions impair sarcomeric Z-disk of XXXX via calpain pathway.

@entity3396 @entity75 @entity42498 @entity116 @entity121 @entity130
The aim of this study was to determine whether or not over-activation of calpains during running exercise or tetanic contractions was a major factor to induce @entity75 in @entity121 . Relationship between the degrees of desmin degradation and @entity75 was also elucidated. We observed ultrastructural changes in soleus muscle fibers after 4-week unloading with or without running exercise. Calpain activity and desmin degradation were measured in atrophic soleus muscles before or after repeated @entity116 in vitro. @entity3396 activity was progressively increased and desmin degradation was correspondingly elevated in 1-, 2-, and 4-week of unloaded soleus muscles. @entity3396 activity and desmin degradation had an additional increase in unloaded soleus muscles after repeated @entity116 in vitro. @entity42498 , an inhibitor of calpains, reduced calpain activity and desmin degradation during tetanic contractions in unloaded soleus muscles. The 4-week unloading decreased the width of myofibrils and Z-disk in soleus fibers. After running exercise in unloaded group, Z-disks of adjacent myofibrils were not well in register but instead were longitudinally displaced. Calpain inhibition compromised exercise-induced misalignment of the Z-disks in @entity121 . These results suggest that tetanic contractions induce an over-activation of calpains which lead to higher degrees of desmin degradation in unloaded soleus muscle. Desmin degradation may loose connections between adjacent myofibrils, whereas running exercise results in @entity130 in unloaded soleus muscle.
