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

[pKZ1マウスでの染色体内組換えに対する900MHz無線周波放射ばく露の影響] med./bio.

Effect of exposure to 900 MHz radiofrequency radiation on intrachromosomal recombination in pKZ1 mice

著者: Sykes PJ, McCallum BD, Bangay MJ, Hooker AM, Morley AA
掲載誌: Radiat Res 2001; 156 (5) Pt 1: 495-502
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この研究は、「携帯電話からの無線周波（RF）放射には直接的な遺伝毒性はないが、細胞DNAの下流影響を与える可能性がある」との仮説を検証した。pKZ1組換え突然変異誘発マウスモデルにおいて、脾臓の体細胞内の染色体内組換えに対する4W / kgのパルス化（パルス繰り返し周波数217 Hz、パルス幅0.6 ms）した900MHz RF放射の影響を調べた。pKZ1マウスの脾臓組織での体細胞内組換え反転事象は、導入遺伝子lacZが反転事象を起こした細胞で見られる大腸菌β-ガラクトシダーゼタンパク質の組織化学的染色によって検出された。pKZ1マウスへのばく露は、毎日30分間、1、5、または25日間継続した。最後のばく露から3日後、脾臓切片でのDNA反転事象スクリーニング検査を行った。その結果、1日および5日のばく露群では対照群との間に有意差はなかったが、25日ばく露群では、自然発生頻度を下回る反転の有意な減少が見られた、と報告している。ただし、実験されたマウスの数が少ないため（n = 10またはn = 20）、より多くの動物での再検証が必要であると考察している。

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研究目的（著者による）

The pKZ1 recombination mutagenesis model was used to determine if exposure to radiofrequency radiation (whole-body SAR 4 W/kg) would induce somatic intrachromosomal recombination in spleen tissue. The pKZ1 recombination mutagenesis model enabels detection of somatic intrachromosomal recombination inversion events in response to DNA-damaging agents.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 900 MHz
Modulation type: pulsed
ばく露時間: repeated daily exposure for 30 min/day for 1, 5 or 25 days (5 days/week)
  • SAR: 4 W/kg average over mass (whole body)

ばく露1

主たる特性
周波数 900 MHz
タイプ
  • electromagnetic field
特性
  • guided field
ばく露時間 repeated daily exposure for 30 min/day for 1, 5 or 25 days (5 days/week)
Additional information plane-wave fields
Modulation
Modulation type pulsed
Pulse width 0.6 ms
Repetition frequency 217 Hz
ばく露装置
ばく露の発生源／構造
チャンバの詳細 The waveguide made of aluminium was a WG3 with a rectangular cross section with external dimensions of 296 mm x 150 mm and a length of 1700 mm. Coaxial to waveguide E-field exciter antennae were built into each end. The RF radiation received by the antenna at the other end of the waveguide was dissipated in a resistive high-power coaxial attenuator. Two tuning screws allowed to minimize the amount of reflected energy.
ばく露装置の詳細 The waveguide had 13 access ports aligned along its length and contained a solid block of Styrofoam that had 13 shaped polycarbonate tubes glued into it. The tubes had bayonet connectors that received and locked the mouse holders into position. The mouse holder tubes (length 173 mm; diameter 32 mm inside, 36 mm outside) made of polycarbonate enabled restraint of a 30-g mouse. The capsules were fully contained except for the hole in the capsule near the nose of the mouse for letting in the air.
Additional information The mice in the multiple-exposure experiments were placed randomly in the waveguide to average out any variations in SAR along the waveguide. Matched sham-exposed mice were placed in the exposure apparatus with the air flow on but no RF radiation for the same period as the treated mice.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 4 W/kg average over mass 測定値および計算値 whole body -
測定および計算の詳細

Measurements of transmitted, received and reflected powers were made using an RF power meter with a power sensor and associated attenuator connected to a directional coupler. Less than 2% of the transmitted energy was lost in the waveguide when there were no animals present, and negligible (40 dBµV/m) RF-radiation energy leaked from the apparatus. A detection diode connected to an oscilloscope enabled the monitoring of the pulse waveform. Two methods were used to determine the SAR received by the animals: The first method used a power-loss equation. Power measurements were performed on the waveguide, with and without up to ten animals or phantoms present. The second method was to measure the temperature increase in mouse phantoms filled with semi-liquid material that had dielectric properties similar to muscle tissue. Both measurement methods gave very similar results, with average calculated SARs of 4 W/kg and 3.3 W/kg, respectively.

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:
研究対象とした臓器系:
調査の時期:
  • ばく露中
  • ばく露後

研究の主なアウトカム（著者による）

There was no significant difference between the control and treated animals in the 1- and 5-day group. But there was a significant reduction in inversions below the spontaneous frequency in the 25-day group. The results suggest that exposure to radiofrequency radiation can lead to a perturbation in recombination frequency which may have implications for recombination repair of DNA.

研究の種別:

研究助成