Cellular and molecular responses to power-frequency electromagnetic fields.

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We investigated the change in gene expression of the stress protein, i.e., the heat shock protein in this study, under a high intensity of extremely low frequency (ELF) magnet field, and as a positive control, we investigated the effect of heat processing. In addition, we also studied a modifying effect of the magnetic field on gene expression of the heat shock protein under treatment of combination of the magnetic field and heat processing.1. The study on the heat shock protein was performed using HSP70, a typical heat shock protein, which reacts to numerous stresses including heat shock and expresses transiently. Goodman et al. (1997) reported ESP70 induction by ELF magnetic field exposure, however, the data at the level of μT were obtained and negative counterarguments were published. In this study, we investigated whether the exposure to a high magnetic intensity of ELF magnet field produces an effect on induction of the heat shock protein or not using human leukemia-derived cells (HL60) that Goodman et al. used. No induction of HSP70 protein expression was observed 24 hours after exposure to the 50 mT ELF magnetic field.2. As a positive control, we investigated the effect of heat processing. In addition, we also studied a modifying effect of the magnetic field on gene expression of the heat shock protein under treatment of combination of the ELF magnetic field and heat processing. Under a mild heat shock (40 - 42 ℃), induction of HSP70 protein expression was observed in HL60 cells. After combined treatment of this heat processing and exposure to the 50 mT ELF magnetic field, the level of HSP70 protein expression was lower than that under treatment of heat shock alone, which indicated that the ELF magnetic field inhibited the HSP70 protein expression. These results suggested that a high intensity of ELF magnetic field exaggerated the negative feedback action against the HSP70 expression induced by the heat shock and inhibited the HSP70 expression.