The Effects of Low-Frequency Magnetic Fields on DNA Unscheduled Synthesis Induced by Methylnitro-NitrosoguanidineIn Vitro

Abstract

Exposure to extremely low and low frequency electromagnetic fields (ELF and LF EMF) has been reported to induce potent carcinogenic effects and adverse pregnancy outcomes. DNA damage may be an EMF target site. This study investigates both 50 Hz and 15.6 kHz magnetic fields on DNA damagehepair in the normal human amniotic FL cell. The test of unscheduled DNA synthesis (UDS) was utilized. In view of the weak effects of the magnetic fields, FL cells were simultaneously treated with methylnitro-nitrosoguanidine (MNNG), a known carcinogen. FL cells were exposed to a 50 Hz sinusoidal magnetic field at 0.3,1.0, and 5.0 mT as well as a 16.5 kHz pulsed magnetic field at 4 and 40 μT (p-p), respectively, for 72 h. The results showed that 50 Hz magnetic field led to nonlinear dose-dependent elevations of DNA damage (exposure to 1 mT increased DNA damage in the presence and absence of MNNG, exposure to 0.3 mT could enhance the effect of MNNG below the threshold concentration, but exposure to 5 mT exerted no influence). In addition, a 15.6 kHz field at 40 μT (p-p) could enhance MNNG inducing DNA damage in FL cells and no effect at 4 μT (p-p) was found, which suggests that very weak genotoxic effects of 15.6 kHz PMF may be revealed and enhanced in combination with a carcinogen.Further experiments should be conducted to observe whether so-called “intensity windows” exist in the biological effects of ELF.