Fifty-Hertz low frequency magnetic field modifies sarcoplasmic reticulum function

Abstract

Among the putative mechanisms, by which extremely low frequency magnetic field (ELF-MF) modify calcium metabolism is that of affecting Ca2+ fluxes across cell membrane or internal Ca2+ stores. To test this hypothesis, whether ELF MF can modulate Ca2+ fluxes of isolated skeletal muscle sarcoplasmic reticulum vesicles (SR) was investigated in the present study. The Ca2+ transport and Ca2+-Mg2+-ATPase activity were observed by means of dynamic Ca2+ dye spectrum, the function of ryanodine receptor (RyR1) was monitored by [3H]-ryanodine binding assay. The membrane fluidity of SR was measured by fluorescence polarization. 50 Hz 0.4 mT MF exposure for 30 min led to a significant decrease in the Ca2+ uptake initial rate and Ca2+-Mg2+-ATPase activity compared to sham exposed SR. These results strongly suggest that prevention of SR Ca2+ uptake by ELF MF exposure was due to the inhibition of Ca2+-Mg2+- ATPase activity, and the increase of SR Ca2+ release was due to the activation of RyR1.