報告書番号

V05013

タイトル（和文）

中間周波磁界の生物影響評価 --酵母細胞を用いた遺伝子変換への影響の評価--

タイトル（英文）

Biological effects of intermediate frequency magnetic field-evaluation of gene conversion by using yeast test strain-

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究では、真核生物である酵母(XD83株)を用いた遺伝子変換試験により中間周波磁界の遺伝毒性およびDNA損傷修復への影響の有無について評価した。2kHzで910μT（国際ガイドラインの146倍）、20kHzで1.1mT（同176倍）、60Hzで110μT（同18倍）の磁界を、それぞれ48時間曝露した。磁界曝露群と曝露していない対照群との間の変異コロニー数を測定し、t-検定によりコロニー数の増減を統計的に評価した。その結果、いずれの周波数帯の磁界曝露に対しても、統計的に有意なコロニー数の変化は見られなかった。また、紫外線照射により遺伝子変換を誘発した細胞に対し磁界を曝露し、DNA損傷修復への影響を評価したところ、磁界曝露による有意なコロニー数の変化は見られなかった。これらのことから、本研究で検討した中間周波磁界は、酵母細胞の遺伝子変換およびDNA損傷修復に影響しないことがわかった。

概要 （英文）

In contrast to extremely low frequency and radio frequency electromagnetic fields (EMF), the biological effects of intermediate frequency (IF; 300Hz to 10MHz) EMF have not been studied very well. In our previous studies, we have reported the novel exposure system which can generate strong IF MFs of 0.91mTrms (146 time greater than ICNIRP guideline) at 2kHz, 1.1mTrms (176 times) at 20kHz and 0.11mTrms (18 times) at 60kHz of IF magnetic fields (MFs) for in vitro research. We also reported that the exposure of the IF MFs did not have mutagenic or co-mutagenic potential in bacterial mutation tests. The mutation test was powerful to detect point mutation, but the test could not detect other genotoxic abnormality found in eukaryotic cells, such as gene conversion. In this study, we have investigated the effects of the IF MFs on the gene conversion in yeast. The yeast test strain, XD83, was chosen to estimate the effects of the MF exposure on gene conversion and DNA damage repair caused by UV radiation. For the gene conversion tests, the yeast test strain was exposed to MFs of 0.91mTrms at 2kHz, 1.1mTrms at 20kHz or 0.11mTrms at 60kHz, for 48h at 30ｰC. The rate of gene conversion was estimated by counting revertant colonies. The ratio of the colony number between MF exposed and unexposed control groups were mostly in the range from 0.8 to 1.2. In statistical analysis, neither significant nor reproducible difference was found between the mutation rates for all MF exposure conditions. To examine the effect on DNA damage repair, the yeast strain has been exposed to each MF after UV-radiation which can increase the rate of gene conversion. In statistical analysis, neither significant nor reproducible difference was found between the rates for all MF exposure conditions. These results indicated that the strong IF MFs did not induce gene conversion and did not affect DNA damage repair system in eukaryote.

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