報告書番号

V06007

タイトル（和文）

中間周波磁界の生物影響評価-哺乳類細胞を用いた小核試験による遺伝毒性評価-

タイトル（英文）

Effect of Intermediate Frequency Magnetic Fields on Micronucleus Formation in Mammalian Cell Line

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、哺乳類培養細胞V79を用い、小核試験により中間周波磁界の遺伝毒性の有無について評価した。2kHzで0.91mTrms（国際ガイドラインの146倍）、20kHzで1.1mTrms（同176倍）、60Hzで0.11mTrms（同18倍）の磁界を、それぞれ24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で、二核細胞数とこのうち小核を有する細胞数を計数し小核形成率を求め、t検定によりその差を統計学的に評価した。その結果、いずれの周波数帯の磁界曝露に対しても、統計学的に有意な小核形成率の差は見られなかった。また、変異原であるMMCを磁界と同時曝露し、小核形成の誘発過程に影響するか評価したところ、磁界曝露による再現性のある有意な小核形成率の差は見られなかった。これらのことから、本研究で検討した高い磁束密度の中間周波磁界は、哺乳類細胞の小核形成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 times 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 have also reported that the exposure of the IF MFs did not have mutagenic, co-mutagenic or gene conversion potentials in microbial genotoxicity tests. In this study, we have investigated the effects of the IF MFs on micronucleus formation in a mammalian cell line. The Chinese hamster V79 cell was chosen to estimate the effects of the MF exposure on micronucleus formation and DNA damage repair caused by mitomycin C (MMC). The V79 cell was exposed to MFs of 0.91mTrms at 2kHz, 1.1mTrms at 20kHz or 0.11mTrms at 60kHz, for 24h at 37C in 5% carbon dioxide. Ratse of micronucleus formation were determined as the proportion of binucleus cells with micronucleus to the total number of binucleus cells. The ratio of micronucleus formation rates 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 micronucleus formation rates for all MF exposure conditions. To examine the effect on DNA damage, V79 cells have been exposed to each MF with MMC which potentiates micronucleus formation. In statistical analysis, two cases of 2kHz MF exposure with MMC showed significant differences, however the differences were very small and opposite directions each other. Neither significant nor reproducible difference was found between the rates for all MF exposure conditions. These results indicated that the strong IF MFs used in this study did not induce micronucleus formation and did not affect DNA damage by MMC or DNA damage repair system in mammalian cells.

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