The action of 50 Hz magnetic and electric fields upon cell proliferation and cyclic AMP content of cultured mammalian cells

Abstract

Mouse fibroblasts were treated for 1 h with sinusoidal 50 Hz magnetic or electric fields. For magnetic field exposure, an iron magnet with air gap and an open solenoid were used. The electric field was applied to the cells cultured on a membraneous substratum via electrodes immersed into the medium below and above the cultures. After an additional 6 h of field-free incubation, cell proliferation and cell cycle effects were measured. The magnetic field of the iron magnet (2 mT flux density) caused a small but statistically significant decrease in the mean DNA content of the exposed cell population, whereas the electric field (0.25 mA/cm 2 current density, corresponding to approximately 70 mV/cm field strength) acted in the opposite way. Cell cycle analysis revealed a slight but significant accumula- tion of cells in the G 1 phase when exposed to the magnetic field of the iron magnet in accordance with the changes of the mean DNA value, while an accumulation in the S and G 2 + M phases was obtained with the electric field. Exposure to a 2 mT magnetic field in the solenoid failed to induce unequivocal changes in the mean DNA content and cycle distribution which, based on the above results, was attributed to the simultaneous but opposite action of the magnetic field and the electric field in this open device. Cell numbers were reduced to 90% of the control values in most experiments. The intracellular levels of cyclic adenosine monophosphate (cAMP) were increased to approximately 120% of the control figures after 5 min exposure to the electric or magnetic field. This suggests that the action of low-frequency electromagnetic fields proceeds via second messenger dependent processes originating from signals at the cell membrane.