Correlation of magnetic AC field on cardiac myocyte Ca²⁺ transients at different magnetic DC levels

The purpose of this study was to determine the effect of extremely low frequency and weak magnetic fields (WMF) on cardiac myocyte Ca²⁺ transients, and to explore the involvement of potassium channels under the WMF effect. In addition, we aimed to find a physical explanation for the effect of WMF on cardiac myocyte Ca²⁺ transients. Indo-1 loaded cells, which were exposed to a WMF at 16Hz and 40nT, demonstrated a 75±4% reduction in cytosolic Ca²⁺ transients versus control. Treatment with the K_ATP channel blocker, glibenclamide, followed by WMF at 16Hz exposure, blocked the reduction in cytosolic calcium transients while treatment with pinacidil, a K_ATP channel opener, or chromanol 293B, a selective potassium channel blocker of the delayed rectifier K⁺ channels, did not inhibit the effect. Based on these finding and the ion cyclotron resonance frequency theory, we further investigated the effect of WMF by changing the direct current (DC) magnetic field (B₀). When operating different DC magnetic fields we showed that the WMF value changed correspondingly: for B₀=44.5μT, the effect was observed at 17.05Hz; for B₀=46.5μT, the effect was observed at 18.15Hz; and for B₀=49μT the effect was observed at 19.1Hz. We can conclude that the effect of WMF on Ca²⁺ transients depends on the DC magnetic field level.