Rapid decrease in active tension generated by C2C12 myotubes after termination of artificial exercise
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We found that the active tension of C2C12 myotubes that had been subjected to artificial exercise for ~10 days decreased rapidly after termination of the artificial exercise. When differentiated C2C12 myotubes were subjected to continuous 1 Hz artificial exercise for ~10 days, the active tension increased to ~4× compared to that before application of the artificial exercise, as reported previously. On termination of artificial exercise, the active tension decreased rapidly, the level reaching that before application of the artificial exercise within 8 h. Concomitant with the decrease in the active tension, an increase in the amount of ubiquitinated proteins was observed. Real time RT–PCR revealed that the expression of several genes associated with atrophy, namely Smc6, Vegfa, Jarid2, Kitl, Cds2, Inmt, Fasn, Neurl, Topors, and Cul2, were also changed after termination of artificial exercise. These results indicate that termination of artificial exercise induced atrophy-like responses of C2C12 myotubes. Here we found that during the decrease in active tension, the sarcomere structure, especially the thin filament structure, decayed rapidly after termination of artificial exercise. On reapplication of the artificial exercise, the active tension was restored rapidly, within 8 h, concomitant with reformation of the sarcomere structure. These results indicate that disassembly of the sarcomere structure may be one of the reasons for the active tension decrease during disuse muscle atrophy.
KeywordsC2C12 Muscle Exercise Thin filament Active tension
The authors thank T. Nedachi for critical reading of the manuscript, and Y. Morioka and A. Kondo for the technical assistance.
- Bodine SC, Latres E, Baumhueter S, Lai VK, Nunez L, Clarke BA, Poueymirou WT, Panaro FJ, Na E, Dharmarajan K, Pan ZQ, Valenzuela DM, DeChiara TM, Stitt TN, Yancopoulos GD, Glass DJ (2001) Identification of ubiquitin ligases required for skeletal muscle atrophy. Science 294(5547):1704–1708CrossRefPubMedGoogle Scholar
- Gibson JN, Halliday D, Morrison WL, Stoward PJ, Hornsby GA, Watt PW, Murdoch G, Rennie MJ (1987) Decrease in human quadriceps muscle protein turnover consequent upon leg immobilization. Clin Sci (Lond) 72(4):503–509Google Scholar