Aims: 

Skeletal myocytes exhibit a remarkable capacity to adapt their properties in response to altered functional demands. Such adaptations can be triggered in vitro, e.g., by electrical stimulation of cultured myocytes. Whereas changes in the expression of contractile proteins and metabolic enzymes in response to electrical stimulation are well understood, very little is known about possible adaptations in the electrophysiological properties of skeletal myocytes. In this study, we investigated the effects of electrical stimulation on the properties of currents through voltage-gated calcium channels of skeletal myocytes.

Methods: 

Mouse C2C12 skeletal myocytes were electrically stimulated continuously for up to two weeks at a frequency of one Hertz. Thereafter, their barium current properties were detected using the whole cell patch clamp technique, and compared with those of control cells. Results:

Electrical stimulation of skeletal myocytes significantly speeded the activation kinetics of their calcium channels. In addition, channel activation seemed to consist of a fast and a slow component in many electrically stimulated myocytes, whereas in control cells, the slow component predominated.

Conclusion: 

Chronic electrical stimulation alters the properties of currents through voltage-gated calcium channels in skeletal myocytes. This could be explained by an up-regulation of the cardiac isoform of the L-type calcium channel in response to electrical stimulation.

Supported by Austrian FWF (P19352-B11)