報告書番号

V09021

タイトル（和文）

中間周波磁界の生物影響評価－形質転換試験によるプロモーター活性の評価－

タイトル（英文）

Effect of Intermediate Frequency Magnetic Fields on Promoter or Co-Promoter Potentials by in vitro Transformation Assay using Bhas 42 cell

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、がん遺伝子であるv-Ha-ras遺伝子が導入されたBhas42細胞を用いた形質転換試験により、中間周波磁界のプロモーター活性およびコプロモーター活性の有無について評価した。2kHzで0.91mT(rms）（国際ガイドラインの146倍）、20kHzで1.1mT(rms）（同176倍）、60Hzで0.11mT(rms）（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、細胞の形質転換に由来するフォーカスを計数し、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、統計学的に有意なフォーカス数の差は見られなかった。また、既知のプロモーターであるTPAを磁界と同時曝露し、フォーカスの誘発過程に影響するか評価したところ、磁界曝露による統計学的に有意なフォーカス数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、プロモーター活性およびコプロモーター活性を持たないことが示された。

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 magnetic fields (MFs) of 0.91mT(rms)(146 times greater than ICNIRP guidelines for public) at 2kHz, 1.1mT(rms) (176 times) at 20kHz and 0.11mT(rms) (18 times) at 60kHz of IF MFs for in vitro research. We have also reported that the exposure of the IF MFs did not have genotoxic potentials which are mutagenic, comutagenic and/or gene conversion potentials in microbial genotoxicity tests, or micronucleus formation or chromosomal aberration in a mammalian cell line. In this study, we have investigated the effects of the IF MFs on promotion or copromotion potentials in a transformation assay by using Bhas42 cell. The assay can detect promotion activity which can relate with nongenotoxic carcinogenesis. The Bhas 42 cells were exposed to MFs of 0.91mT(rms) at 2kHz, 1.1mT(rms)s at 20kHz or 0.11mT(rms) at 60kHz, for 10days at 37 degree Celsius in 5% carbon dioxide from day 4 to day 10. After the MF exposure, the cells were incubated for 7 days to make a focus by transformed cells. The number of focus was counted after 21 days total incubation. To examine the effects on copromotion, the cells were exposed to each MF with TPA which is a typical nongenotoxic carcinogen, a tumor promoter. In statistical analysis, neither significant nor reproducible difference in the focus number was found between exposure and control groups under the all MF exposure conditions. These results indicated that the strong IF MFs used in this study did not have promotion or copromotion potentials in vitro.

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