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

[広範囲のSARを用いたラジオ周波電磁界の連続および間欠ばく露の細胞成長､生存、細胞周期分布に対する影響] med./bio.

Effects of continuous and intermittent exposure to RF fields with a wide range of SARs on cell growth, survival, and cell cycle distribution

著者: Takashima Y, Hirose H, Koyama S, Suzuki Y, Taki M, Miyakoshi J
掲載誌: Bioelectromagnetics 2006; 27 (5): 392-400
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この研究は、無線周波（RF）電磁界ばく露による基本的な細胞応答（細胞増殖、生存、細胞周期分布など）への影響を、SARを広範囲に変化させて評価した。さらに、高レベルのSARにおいて、連続波と断続波のばく露の影響を比較した。2.45 GHzのRF電磁界ばく露装置を用いて、0.05〜1500 W / kgのSARで実験した。その結果、0.05〜100 W / kgのSARで、連続波RF電磁界への2時間ばく露の場合、細胞増殖率、生存率、および細胞周期分布は影響を受けなかった；200 W / kgでは、細胞増殖率が抑制され、細胞生存率が低下した；平均SARが100 W / kg で、ピークSARが300 W / kg（pk）、900 W / kg（pk）、1500 W / kg（pk）の断続波RF電磁界ばく露の場合、これらの条件の断続波ばく露と100 W / kgの連続波ばく露との間に有意差は観察されなかった；50 W / kgのSARでの2時間ばく露の場合、細胞周囲の培地の温度は39.1 ℃に上昇し、100 W / kgのばく露では41.0 ℃に、200 W / kgのばく露では44.1 °Cに上昇した；RF電磁界ばく露により培地が加熱され、その熱効果は平均SARに依存するため、得られた知見から、増殖への影響が熱効果により生じることが示された、と報告している。

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研究目的（著者による）

To study cell growth, cell survival, and cell cycle distribution following exposure to a wide range of SAR values. Furthermore, to determine whether non-thermal effects of radiofrequency irradiation influence cell proliferation at SAR levels at which the thermal effects are evident, the authors compared the effects of continuous exposure and intermittent exposure at high SAR values.

詳細情報

Temperature controls were performed at 39, 40, 41, 42, 43, and 44°C.

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: 0.05 W/kg maximum
  • SAR: 0.5 W/kg maximum
  • SAR: 5 W/kg maximum
  • SAR: 50 W/kg maximum
  • SAR: 100 W/kg maximum
  • SAR: 200 W/kg maximum
ばく露2: 2.45 GHz
Modulation type: CW
ばく露時間: intermittent for 2 h, 1 s on/x s off, see exposure parameters
  • SAR: 50 W/kg mean
  • SAR: 300 W/kg peak (5 s off)
  • SAR: 900 W/kg peak (17 s off)
  • SAR: 1,500 W/kg peak (29 s off)
ばく露3: 2.45 GHz
Modulation type: CW
ばく露時間: intermittent for 2 h, 1 s on/x s off, see exposure parameters
  • SAR: 100 W/kg mean
  • SAR: 300 W/kg peak (2 s off)
  • SAR: 900 W/kg peak (8 s off)
  • SAR: 1,500 W/kg peak (14 s off)

ばく露1

主たる特性
周波数 2.45 GHz
タイプ
  • electromagnetic 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
  • rectangular, 110 mm wide x 55 mm high x 310 mm long, operating in TE10 mode
チャンバの詳細 The exposure unit was mounted in an incubator.
ばく露装置の詳細 A culture dish in which the medium stood 8 mm high was placed on two slits in the top wall of the waveguide. The slits were optimized with a pinched shape to increase the effective exposure area and enhance the uniformity of the electric field and the SAR distribution in the medium. One end of the waveguide was terminated with a short-circuiting plate to generate standing waves.
Sham exposure A sham exposure was conducted.
Additional information The temperatures of the medium at the maximum SAR position measured using a fibre optic thermometer rose to 39.1 °C, 41.0 °C, and 44.1 °C after exposure to 50, 100, and 200 W/kg, respectively, for 2 h at an ambient temperature of 37 °C. Cells for raised temperature control were incubated at 39, 40, 41, 42, 43, and 44 °C in a conventional incubator for the same time periods.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 0.05 W/kg maximum 計算値 - -
SAR 0.5 W/kg maximum 計算値 - -
SAR 5 W/kg maximum 計算値 - -
SAR 50 W/kg maximum 計算値 - -
SAR 100 W/kg maximum 計算値 - -
SAR 200 W/kg maximum 計算値 - -
Additional parameter details

Rectangular culture dishes divided into four compartments were used. Compartments 2 and 4 provided 80 and 85% of the maximum SAR value obtained in compartment 3, whereas in compartment 1, the SAR was less than 1% of the maximum value.

測定および計算の詳細

The incident and reflected powers were monitored by power sensors. SAR distribution was calculated using the FDTD method and confirmed experimentally by measuring the temperature increase in the medium over a short period following acute exposure using a DASY 3 positioning system with a thermistor probe.

ばく露2

主たる特性
周波数 2.45 GHz
タイプ
  • electromagnetic field
ばく露時間 intermittent for 2 h, 1 s on/x s off, see exposure parameters
Modulation
Modulation type CW
ばく露装置
ばく露の発生源／構造
  • E1と同じ装置
Sham exposure A sham exposure was conducted.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 50 W/kg mean 計算値 - -
SAR 300 W/kg peak 計算値 - 5 s off
SAR 900 W/kg peak 計算値 - 17 s off
SAR 1,500 W/kg peak 計算値 - 29 s off

ばく露3

主たる特性
周波数 2.45 GHz
タイプ
  • electromagnetic field
ばく露時間 intermittent for 2 h, 1 s on/x s off, see exposure parameters
Modulation
Modulation type CW
ばく露装置
ばく露の発生源／構造
  • E1と同じ装置
Sham exposure A sham exposure was conducted.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 100 W/kg mean 計算値 - -
SAR 300 W/kg peak 計算値 - 2 s off
SAR 900 W/kg peak 計算値 - 8 s off
SAR 1,500 W/kg peak 計算値 - 14 s off

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

研究対象とした生物試料:
調査の時期:
  • ばく露後

研究の主なアウトカム（著者による）

When cells were exposed to a continuous radiofrequency electromagnetic field at SAR values from 0.05 to 100 W/kg for 2 h (field 1), cell growth, cell survival, and cell cycle distribution were not affected. At 200 W/kg, the cell growth was suppressed and cell survival decreased.
When the cells were exposed to an intermittent radiofrequency electromagnetic field at 300 W/kgpeak, 900 W/kgpeak and 1500 W/kgpeak (100 W/kgmean; cf. field 3), no significant differences in cell growth and cell survival were found.
Cells incubated at 43 and 44°C (temperature control) exhibited marked inhibition of cell proliferation.
When cells were exposed (continuous or intermittent) to a SAR of 50 W/kg for 2 h, the temperature of the medium rose to 39.1°C, 100 W/kg exposure increased the temperature to 41.0°C, and 200 W/kg exposure increased the temperature to 44.1°C.
Thus, exposure to radiofrequency exposure results in heating of the medium, and the thermal effect depended on the mean SAR. Hence, these results suggest that the cell proliferation disorder is caused by the thermal effect.

研究の種別:

研究助成

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