DNA-DAMAGE IN RAT-BRAIN CELLS AFTER IN-VIVO EXPOSURE TO 2450 MHZ ELECTROMAGNETIC-RADIATION AND VARIOUS METHODS OF EUTHANASIA

The present study was done to confirm the reported observation that lo w-intensity acute exposure to 2450 MHz radiation causes DNA single-str and breaks (Lai and Singh, Bioelectromagnetics 16, 207-210, 1995). Mal e Sprague-Dawley rats weighing approximately 250 g were irradiated wit h 2450 MHz continuous-wave (CW) microwaves for 2 h at a specific absor ption rate of 1.2 W/kg in a cylindrical waveguide system (Guy et al., Radio Sci. 14, 63-74, 1979). There was no associated rise in the core body temperature of the rats. After the irradiation or sham treatments , rats were euthanized by either CO2 asphyxia or decapitation by guill otine (eight pairs of animals per euthanasia group). After euthanasia the brains were removed and immediately immersed in cold Ames medium a nd the cells of the cerebral cortex and the hippocampus were dissociat ed separately and subjected to the alkaline comet assay. Irrespective of whether the rats were euthanized by CO2 asphyxia or decapitated by guillotine, no significant differences were observed between either th e comet length or the normalized comet moment of cells from either the cerebral cortex or the hippocampus of sham-treated rats and those fro m the irradiated rats. However, the data for the rats asphyxiated with CO2 showed more intrinsic DNA damage and more experiment-to-experimen t variation than did the data for rats euthanized by guillotine. There fore, the guillotine method of euthanasia is the most appropriate in s tudies relating to DNA damage. Furthermore, we did not confirm the obs ervation that DNA damage is produced in cells of the rat cerebral cort ex or the hippocampus after a 2-h exposure to 2450 MHz CW microwaves o r at 4 h after the exposure. (C) 1998 by Radiation Research Society.