研究のタイプ: 医学／生物学の研究 (experimental study)

[CHO-K1細胞での小核形成に対する広範囲のSARをもたらす2.45GHz電磁界の影響] med./bio.

Effects of 2.45-GHz electromagnetic fields with a wide range of SARs on micronucleus formation in CHO-K1 cells

著者: Koyama S, Isozumi Y, Suzuki Y, Taki M, Miyakoshi J
掲載誌: ScientificWorldJournal 2004; 4: 29-40
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この研究は、チャイニーズハムスター卵巣細胞CHO-K1の小核（MN）形成に対する2.45 GHz 電磁界（EMF）の影響を調べた。MN形成は、細胞分裂中に染色体切断または紡錘体阻害によって誘導され、細胞損傷を引き起こすものである。また、高周波電磁界ばく露は温度上昇を引き起こすので、MN形成に対する熱の影響も調べた。CHO-K1細胞に、平均SARレベル5、10、20、50、100、および200 W / kgの2.45 GHz EMFばく露を2時間与え、これらの細胞への影響を擬似ばく露対照と比較した。陽性対照として、ブレオマイシン単独ばく露または2.45 GHz EMFとブレオマイシンの組み合わせばく露も実施された。熱ばく露は、37、38、39、40、41、および42℃の温度で実施された。その結果、50W / kg未満のSARで2.45 GHz EMFばく露された細胞のMN頻度には擬似ばく露対照との差がなかった；一方、SARが100および200 W / kgの場合、擬似ばく露対照と比較して有意に高かった；2.45 GHz EMFばく露とブレオマイシン処理の組み合わせによる影響は見られなかった；38〜42℃での熱処理で、MN頻度は温度依存的に増加した； SARの増加が温度の上昇を引き起こし、これが2.45 GHz EMFばく露によるMN形成増加に関連している可能性も示された、と報告している。

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研究目的（著者による）

This study was conducted to investigate the effects of 2.45 GHz electromagnetic fields with a wide range of specific absorption rates on micronucleus formation in a cell line.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 2.45 GHz
Modulation type: CW
ばく露時間: continuous for 2 h
  • SAR: 5 W/kg mean
  • SAR: 10 W/kg mean
  • SAR: 20 W/kg mean
  • SAR: 50 W/kg mean
  • SAR: 100 W/kg mean
  • SAR: 200 W/kg mean

ばく露1

主たる特性
周波数 2.45 GHz
タイプ
  • electromagnetic field
波形
  • sinusoidal
特性
  • guided field
ばく露時間 continuous for 2 h
Modulation
Modulation type CW
ばく露装置
ばく露の発生源／構造
  • 導波管
  • 110 x 55 x 310 mm (W x H x L), TE10 mode
チャンバの詳細 Two rectangular waveguide applicators were placed in an incubator at 37°C with 95% air and 5% CO2. One end of the waveguide was terminated with a short-circuiting plate to generate standing waves.
ばく露装置の詳細 Cells in culture medium were exposed in a culture dish that was placed on two slits bored into the wider wall of the waveguide. The two slits were pinch shaped which enhanced the coupling of the EMF to increase the effective exposure area. The culture dish was rectangular in shape and divided into four compartments. The thickness of the medium was chosen based on numerical analysis to be 8 mm, which corresponded to half a wavelength in the medium, in order to maximise the SAR at the bottom of the well where the cells were present.
Sham exposure A sham exposure was conducted.
Additional information For sham exposure, the cells were incubated in a conventional incubator. Heat treatment was performed at temperatures of 38, 39, 40, 41, and 42°C. The cells were also treated with bleomycin alone (positive control) or combined with RF exposure or heat.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 5 W/kg mean - - -
SAR 10 W/kg mean - - -
SAR 20 W/kg mean - - -
SAR 50 W/kg mean - - -
SAR 100 W/kg mean - - -
SAR 200 W/kg mean - - -
Additional parameter details

It is not clear from the article, where the indicated average SARs were determined. The maximum SAR appeared at the bottom in the middle of the second compartment from the termination of the waveguide where the coupling with the field was strongest. The maximum SAR values in the adjacent compartments were 80 and 85% of this. The minimum SAR in the fourth compartment from the termination was 1%.

測定および計算の詳細

Power sensors monitored the incident and reflected powers, and the signal generator precisely controlled the incident power. The SAR distribution in the exposure apparatus was calculated using the FDTD method and was measured using a DASY3 system with a thermistor probe. The results of both methods showed good agreement. The temperature of the culture medium was measured during exposure using a fluoroptic temperature probe. It increased from an initial value of 37 °C after about 2000 s to a stable level approximately proportional to the SAR value as shown in a figure. A numerical calculation showed that the temperature distribution was not homogeneous.

ばく露を受けた生物:

方法 影響評価項目／測定パラメータ／方法

研究の主なアウトカム（著者による）

There was no statistically significant effect on micronuleus formation in cells exposed to high frequency electromagnetic fields at specific absorption rates from 5 to 50 W/kg. However, statistically significant increase in micronucleus formation was found in cells exposed to specific absorption rates of 100 and 200 W/kg.
There was no apparent effect of co-exposure (high frequency electromagnetic field exposure plus bleomycin treatment).
The heat treatment revealed micronucleus frequency increase in a temperature-dependent manner. Additionally, the increase in specific absorption rate caused a rise in temperature. Therefore, the observed increases in micronucleus formation were attributed to the temperature rise caused by the high frequency electromagneitc fields.

研究の種別:

研究助成

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