Nakasono Satoshi, Ikehata Masateru, Dateki Minori, Yoshie Sachiko, Shigemitsu Tsukasa, Negishi Tadashi
EMF Environment Sector, Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, Abiko-City, Chiba, Japan.
Mutat Res. 2008 Jan 8;649(1-2):187-200. doi: 10.1016/j.mrgentox.2007.09.003. Epub 2007 Sep 29.
We used bacterial mutation and yeast genotoxicity tests to evaluate the effects of intermediate frequency (IF; 2 kHz, 20 kHz and 60 kHz) magnetic fields (MFs) on mutagenicity, co-mutagenicity and gene conversion. We constructed a Helmholtz type exposure system that generated vertical and sinusoidal IF MFs, such as 0.91 mT at 2 kHz, 1.1 mT at 20 kHz and 0.11 mT at 60 kHz. Mutagenicity, co-mutagenicity and gene conversion assays were performed for each of the three MF exposure conditions. Mutagenicity testing was performed in four strains of Salmonella typhimurium (TA98, TA100, TA1535 and TA1537) and two strains of Escherichia coli (WP2 uvrA and WP2 uvrA/pKM101) to cover a wide spectrum of point mutations. For co-mutagenicity tests, we used four sensitive test strains (TA98, TA100, WP2 uvrA and WP2 uvrA/pKM101) with five chemical mutagens (t-butyl hydroperoxide (BH, a hydroxyl free radical precursor), 2-(2-furyl)-3-(5-nitro-2-furyl) acrylamide (AF2) and N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG, DNA reactive reagents), benz[a]pyrene (BaP) and 2-aminoanthracene (2AA, DNA reactive promutagens). Gene conversion testing was performed in the yeast test strain, Saccharomyces cerevisiae XD83. We also examined the effects on the repair process of DNA damage by UV irradiation. No statistically significant effects were observed between exposed and control groups in any of the genotoxicity tests, indicating that the IF MFs (0.91 mT at 2 kHz, 1.1 mT at 20 kHz or 0.11 mT at 60 kHz) do not have mutagenic or co-mutagenic potentials for the chemical mutagens tested under these experimental conditions. Our findings also indicate that these IF MFs do not induce gene conversion or affect the repair process of DNA damage in eukaryotic cells.
我们使用细菌突变试验和酵母遗传毒性试验来评估中频（IF；2千赫、20千赫和60千赫）磁场（MFs）对致突变性、共突变性和基因转换的影响。我们构建了一个亥姆霍兹型暴露系统，该系统可产生垂直的正弦中频磁场，如2千赫时为0.91毫特斯拉、20千赫时为1.1毫特斯拉、60千赫时为0.11毫特斯拉。针对三种磁场暴露条件中的每一种，都进行了致突变性、共突变性和基因转换测定。致突变性测试在四株鼠伤寒沙门氏菌（TA98、TA100、TA1535和TA1537）和两株大肠杆菌（WP2 uvrA和WP2 uvrA/pKM101）中进行，以涵盖广泛的点突变类型。对于共突变性测试，我们使用了四株敏感测试菌株（TA98、TA100、WP2 uvrA和WP2 uvrA/pKM101）以及五种化学诱变剂（叔丁基过氧化氢（BH，一种羟基自由基前体）、2-（2-呋喃基）-3-（5-硝基-2-呋喃基）丙烯酰胺（AF2）和N-乙基-N'-硝基-N-亚硝基胍（ENNG，DNA反应试剂）、苯并[a]芘（BaP）和2-氨基蒽（2AA，DNA反应性促诱变剂）。基因转换测试在酵母测试菌株酿酒酵母XD83中进行。我们还研究了对紫外线照射引起的DNA损伤修复过程的影响。在任何遗传毒性测试中，暴露组和对照组之间均未观察到统计学上的显著差异，这表明在这些实验条件下，中频磁场（2千赫时为0.91毫特斯拉、20千赫时为1.1毫特斯拉或60千赫时为0.11毫特斯拉）对所测试的化学诱变剂没有致突变或共突变潜力。我们的研究结果还表明，这些中频磁场不会诱导基因转换，也不会影响真核细胞中DNA损伤的修复过程。
