Biophysical effects of high frequency electrical field (4-64 MHz) on muscle fibers in culture

Effects of oscillating electrical fields on living cells depend on the frequency. Electrical field oscillating in the range of MHz can induce cell membrane deformation which may end in cell damage or stimulation. The issue has been studied in red blood cells, but never in excitable cells. In this study we investigated the behaviour of murine muscles and single muscle fibers exposed in vitro to an oscillating electrical field in the MHz range. The commercial set-up Rexonage TM (Telea srl), providing a particular frequency spectrum in the range 4-64MHz that is patented as “quantum molecular resonance stimulation”, was used as a generator of electrical field and a wide range of powers was examined. Muscles or muscle fibers were placed on the bottom of Petri dishes and electrical field was applied between a needle electrode immersed in the medium and movable by means of a micromanipulator and an electrode placed under the bottom of the dish. While high power stimulation produced a fast and well localized cut of the fibers, low power stimulation caused a reversible deformation of the membrane. Such deformation was accompanied by a membrane depolarization and an increase of cytosolic free calcium, which were detected with fluorescent probes. Both the changes of membrane potential and the variations of free calcium concentration strictly followed the time course of electrical field application and removal. In conclusion, the present results demonstrate that excitable cells, such as muscle fibers, respond to the application of high frequency electrical field even when the threshold for action potential is not reached. This might lead to the activation of intracellular signalling pathways even without contraction.