Modulation of structural protein content of the myotendinous junction following eccentric contractions.

The objective of this study was to test the hypothesis that vinculin and talin, two cytoskeletal proteins of the myotendinous junction (MTJ), would be up-regulated following damaging eccentric contractions. Mouse plantar flexor muscles were submitted in situ to three 5 min periods of eccentric contractions. Talin and vinculin content, in vitro contractile properties and MTJ histology were examined at 0, 3, 7, 14, and 28 days post-exercise. The eccentric protocol led to significant decreases in maximum tetanic tension at 0, 3, and 7 days post-protocol. Histological examination did confirm that tissue damage was present at the MTJ where talin and vinculin are highly concentrated. In the type I soleus muscle talin content increased slightly at 7 days post-eccentric protocol compared to SHAM. In the type II plantaris muscle eccentric contraction led to an increase for vinculin and talin contents that was 2-3 fold higher than in the soleus; these significant changes were still present 28 days postexercise. These results show that eccentric contractions can trigger intense protein synthesis activity at the MTJ most likely related to myofibrillogenesis associated with MTJ remodeling.