THE EFFECTS OF LOW-FREQUENCY MAGNETIC-FIELDS ON DNA UNSCHEDULED SYNTHESIS INDUCED BY METHYLNITRO-NITROSOGUANIDINE IN-VITRO

Exposure to extremely low and low frequency electromagnetic fields (EL F 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 damage/repair in the normal human amniotic FL cell. The test of unsch eduled DNA synthesis (UDS) was utilized. In view of the weak effects o f the magnetic fields, FL cells were simultaneously treated with methy lnitro-nitrosoguanidine (MNNG), a known carcinogen. FL cells were expo sed to a 50 Hz sinusoidal magnetic field at 0.3, 1.0, and 5.0 mT as we ll as a 16.5 kHz pulsed magnetic field at 4 and 40 mu T (p-p), respect ively, for 72 h. The results showed that 50 Hz magnetic field led to n onlinear dose-dependent elevations of DNA damage (exposure to 1 mT inc reased 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 mu T (P-P) could enhance MNNG inducing DNA damage in FL ce lls and no effect at 4 mu T (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 conducte d to observe whether so-called ''intensity windows'' exist in the biol ogical effects of ELF.