The Study Of The Effects Of 2450-MHz Microwave On The DNA Damage By Three Chemical Mutagens With Comet Assay And Micronucleus Test In Vitro

1.ObjectivesRadiofrequency fields (RF), especially microwaves (300MHz-300GHz) are a kind of non-ionising radiations which have been widely used in industry, traffic, medicine, radio and television communication as well as in everyday life. Therefore, people are constantly exposed to microwave radiations. These sources of non-ionising radiations cause atmosphere pollution similar to the pollution from various industrial sources. With increasing of the awareness of environmental protection, people are of great concern with a health risk of microwave exposure. A lot of investigations of RF-induced genetic effects in somatic or germ cells have already been conducted in many different cell and animal systems. Different frequencies were studied with emphasis on the 2450-MHz microwave and mobile telephone frequencies. In the investigations using different eukaryotic cell systems in vitro, the both positive and negative resultswere obtained. When some evidence for a genetic effect was reported, this could be ascribed to hyperthermia. As well known, themal effects of microwave may cause irreversible damage. But mis kind effect does not constitute a particular health problem, as protective measure can be taken to prevent excessive exposure. However, the non-memal effect induced by low-level exposure should be the emphasis of microwave investigations. According to majority of the papers, microwaves do not induced genetic effects in vitro and vivo, at least under non-thermal exposure conditions, and seem not to be teratogenic or to be cancinogenic. Thence, it was thought that synergistic investigation of microwave radiation deserves special attention. Indeed, people are exposed to many different environmental physical and chemical factors, and theoretically it may well be that a microwave exposure alone did not result in genetic effects, but this exposure might enhance the mutagenicity, carcinogenicity or teratogenicity of other chemical or physical factors. The objectives of this study are to observe whether there are some synergistic effects between 2450-MHz microwave and three Jpnds of chemical mutagens with comet assay and micronucleus test; and explore its possible mechanism..2.Materials and methods2.1 Microwave exposure systemThe exposure-system was a mechanically modified version of the system described by Garaj. The radiation source was a magnetron, central frequency 2450MHz.The power density of the blood sample was measured by a power meter (Model 8712 survey meter), so thatthe power density of the sample could be controlled at 5.0 mW/cm2. This power density was determined, on the basis of the limited value standard regulated by IRPA (International Radiation Protection Association) in 1983. The exposure-system was kept under controlled temperature conditions at 24 癈 in a dark room. A digital contact thermometer was used to continuously monitor the sample surface temperature. The mean increasing temperature of blood sample was <0.5 癈.2.2 Cell treatment and group 2.2.1 The first partBlood samples were taken from non-smoking young healthy donors (a male and a female), without recent diagnostic or occupational exposure to ionizing or other physical and chemical factors. A 14 ml blood sample was taken with heparin anticoagulant and divided into 10 dose groups. 1 ml whole blood was used for every dose group in comet assay and 0.4 ml whole blood was used for every dose group in micronucleus test. (1) control group (non-microwave and MMC exposure group); (2) microwave radiation group(MW, blood sample was irradiated by 2450MHz microwave for 2h) ; (3) 4 MMC groups, the blood samples were exposed to MMC for 24 h at the final concentrations 0.0125ug/ml, 0.025ug/ml, 0.05ug/ml, 0.1 ug/ml repectively; (4) 4 MW plus MMC groups. Blood samples were first exposed to microwave radiation for 2 h and then treated with MMC for 24h. In micronucleus test, the whole blood were exposed to microwave radiation for 2 h at 26 h before harvesting cells, then were exposed to10MMCfor24h. 2.2.2 Th...