There is a growing concern if the power-line frequency (50/60 Hz) magnetic field (termed in this paper ELF-MF) increases cancer risks. Since one of the major causes of cancer is cellular oxidative stress, whether the ELF-MF increases the oxidative stress is a central problem in the studies on the biological effect of the ELF-MF. Here, we have investigated the effect of 50-Hz sinusoidal magnetic field on the production of O 2 -, the expression of heat shock protein (HSP) 70 and the mitochondrial membrane potential in cell line macrophage RAW264 cells. Macrophages were exposed to or not exposed to 0.1-mT or 0.5-mT, 50-Hz sinusoidal magnetic field and were subjected to (1) assay for O 2 -(2) analysis of the expression of HSP70, and (3) measurement of the mitochondrial membrane potential with a fluorescent indicator. The 50-Hz magnetic field enhanced production of O 2 -and the expression of HSP70, both of which are consistent with previous studies. The exposure to 50-Hz magnetic field decreased mitochondrial membrane potential indicating the diminished activity of mitochondria. The uncoupler of mitochondrial function, carbonyl cyanide p-trifluoromethoxyphenylhydrazone diminished the membrane potential, as expected. On the other hand, it increased the production of O 2 -. The results collectively suggest that the 50-Hz magnetic field diminished the mitochondrial membrane potential, which led to the increase in the production of O 2 -and the expression of HSP70 protein.

Co-stimulation of the cell with LPS and a 50-Hz magnetic field promoted SSB and lowered cell viability, but these were not mediated by LPS-induced NO production.

Bodies are exposed to environmental magnetic fields of low frequency produced by objects such as power lines. A large number of studies have investigated the

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Power-line frequency (50/60 Hz) magnetic fields enhance DNA strand breaks in the cell. In order to understand the molecular mechanism underlying this phenomenon, we analyzed the conversion of plasmid from the supercoiled to the linear form. This conversion is promoted by hydroxyl radical generated by the reaction between Cu 2+ and H 2 O 2 . The plasmid pHSG298 was incubated with 1 μM Cu 2+ and 1 mM H 2 O 2 and exposed to a 1.2 mT, 50-Hz magnetic field for 30, 60, and 90 min. The conversion of supercoiled DNA to linear DNA was analyzed by agarose gel electrophoresis. We found that exposure to the magnetic field for 90 min significantly enhanced the degree of conversion.