Effect of Electric Field Direction on Contractile Movement of Longitudinally Oriented Myotubes Cultured in Vitro

The effect of electric field direction on contraction of longitudinally oriented myotubes has been studied in vitro. The oriented myotubes were made by the cultivation in the vortex flow around a silicone rubber disk in the culture dish swung by a rotating tilted plate at 30 revolutions per minute. C2C12 (Mouse myoblast cell line) cells are cultured in the Dulbecco's Modified Eagle's Medium for seven days. The horse serum was added to differentiate the muscle cells to myotuybes. After the cultivation, periodical electric pulses (1 ms pulse width with a period of 0.1 s) were applied to the medium with a pair of electrodes of platinum wire of 0.2 mm diameter. The myotubes were tetanized, when the electric pulses were applied. The distance between traceable points on a myotube in longitudinal direction was measured during the microscopic observation. Variation was made on the angle between the longitudinal direction of myotube and the direction of the electric field. The experimental results show that the amplitude of contraction is maximized when the direction of the electric field is parallel to the longitudinal direction of myotubes, and that the rate increases when the myotubes are oriented parallel each other.