Increase in nitric oxide and cyclic GMP of rat cerebellum by radio frequency burst-type electromagnetic field radiation.

1. Using rat cerebellum supernatant, the effects of radio frequency (RF) burst-type electromagnetic (EM) field radiation on the production of cyclic GMP were examined under various conditions. The radiation was generated by a generator coil, and set at a 10 MHz radiation frequency, a 50% burst time, a 10 kHz burst rate and a 5 V peak-to-peak generator voltage. 2. When the cerebellum supernatant was incubated with both exogenous L-arginine (nitric oxide (NO) donor) and NADPH, and irradiated by an RF burst-type EM field, the production of cyclic GMP was increased significantly from a level of 21-22 nmol min-1 (g tissue)-1 to 25-26 nmol min-1 (g tissue)-1. By contrast, such an effect was not found when the cerebellum supernatant was irradiated by an RF volley-type EM field. 3. When neither L-arginine nor NADPH were added to the cerebellum supernatant, the production of cyclic GMP was lowered to a level of 6 nmol min-1 (g tissue)-1 and the radiation effect was not found. When the cerebellum supernatant was chelated with EDTA, the production of cyclic GMP was lowered to a level of 7 nmol min-1 (g tissue)-1 and the radiation effect was not found. 4. Incubation with Methylene Blue, a guanylate cyclase inhibitor, lowered the production of cyclic GMP to a level of 10-12 nmol min-1 (g tissue)-1, and the radiation effect did not occur. On incubation with a NO synthase inhibitor, either NG-methyl-L-arginine or N omega-nitro-L-arginine methyl ester, the production of cyclic GMP was lowered to a level of 10-12 nmol min-1 (g tissue)-1 or 5-9 nmol min-1 (g tissue)-1 respectively, and the radiation effect was not observed. 5. Using electrochemical NO probes, the production of NO in the cerebellum supernatant was detected. The concentration of NO increased gradually after the onset of the EM field radiation. The radiation effect persisted, and reached a maximum after the cessation of the radiation. 6. In an in vivo study, the arterioles of the frog web were dilated by the radiation, and this radiation effect was almost completely abolished by the addition of a NO synthase inhibitor. This indicates that radiation activates NO synthase and ultimately induces vasodilatation.