Abstract
Striated muscle has highly ordered periodic structure called sarcomere, which consist of thick and thin filaments. Recent finding indicate that spontaneous Ca2+ transient is important for sarcomere development, but precise mechanism is still unknown. Using C2C12 cells which differentiate into muscle like morphology, we have developed a method to rapidly accelerate sarcomere assembly by applying electric pulse stimulation, which will be useful to study the molecular mechanism of sarcomere development. C2C12 cells were differentiated and electric pulse of 40 V/60 mm, 1 Hz, and 24 ms pulse width was applied at 37°C and 5% CO2, and contraction of myotubes were observed. Myotubes initially did not contract by electric pulse stimulation, but gradually started to contract and the movement reached maximum after 2 hours of stimulation. Application of low frequency stimulation (0.1 Hz) significantly delayed the development of myotubes compared to 1 Hz. Addition of verapamil completely blocked the movement of myotubes. Sarcomere structure observed under confocal microscope also increased in accord with contraction of myotubes although amount of muscle protein did not change significantly. These results indicate that Ca2+ oscillation is important for sarcomere assembly and acceleration of Ca2+ transient enhance muscle development. [Jpn J Physiol 55 Suppl:S122 (2005)]
