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

[3‐クロロ‐4‐(ジクロロメチル)‐5‐ヒドロキシ‐2(5H)‐フラノンによって誘導されるメス Wistarラットの腫瘍に対するラジオ周波照射の影響はない] med./bio.

No effects of radiofrequency radiation on 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone-induced tumorigenesis in female Wistar rats

著者: Heikkinen P, Ernst H, Huuskonen H, Komulainen H, Kumlin T, Maki-Paakkanen J, Puranen L, Juutilainen J
掲載誌: Radiat Res 2006; 166 (2): 397-408
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この研究は、飲料水中の変異原物質MX(3-クロロ-4-（ジクロロメチル）-5-ヒドロキシ-2（5H）-フラノン）によって誘発される腫瘍形成に対する高周波（RF）放射の影響の可能性を評価した。実験の開始時に7週齢のWistar雌ラットを無作為に4群（それぞれn = 72）に分けた。ケージ対照群、RFばく露（全身平均SAR =0.3 W / kg ）＋MX投与群、RFばく露（同0.9 W / kg ）＋MX投与群、RF擬似ばく露＋MX投与群である。MXの投与は、104週間、1日の平均投与量1.7 mg MX / kg体重）で行われた。RFばく露は、1日2時間、週5日で、104週間行われた。実験終了後、3つのMXばく露群のラットに完全な組織病理学検査を行なった。その結果、MXばく露群で観察された腫瘍の種類と発生率は、MXばく露を受けた雌Wistarラットで以前に報告されたものと同様であった；RF放射は、死亡率および全ての腫瘍タイプの臓器特異的発生率に有意な影響を与えなかった；唯一の統計的有意が見られたのは、MX＋高レベルRFばく露群における腸間膜リンパ節の血管腫瘍の発生率が、MX＋RF擬似ばく露群より高かったことである；しかし、追加的にケージ対照群で実施した組織病理学的分析により、この違いは高レベルRFばく露群で発生率が高かったのではなく、RF擬似ばく露群においてこのタイプの腫瘍の発生率が異常に低かったことによることはが示された、と報告している。

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研究目的（著者による）

To study possible effects of radiofrequency irradiation on tumorigenesis induced by the drinking water mutagen 3-chloro-4-dichloromethyl-5-hydroxy-2-5H-furanone (MX) in rats.

詳細情報

MX was given in the drinking water at a concentration of 19 µg/ml.

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, 2 h/day, 5 days/week, for 104 weeks
  • SAR: 0.3 W/kg mean (whole body) (0.07-0.65 W/kg)
  • SAR: 0.9 W/kg mean (whole body) (0.21-1.9 W/kg)

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, 2 h/day, 5 days/week, for 104 weeks
Modulation
Modulation type pulsed
Pulse width 0.577 ms
Repetition frequency 217 Hz
Additional information

continuous transmission of GSM pulses with a pulse period of 4.615 ms
ばく露装置
ばく露の発生源／構造
チャンバの詳細 Nine well ventilated radial transmission line (RTL) exposure chambers were placed in three racks, each rack containing one exposure chamber for each of the three exposure conditions. Each exposure chamber consisted of two parallel circular aluminium plates with 150 cm diameter and 15 cm separation. The edges of the plates were shorted with a metallic wall covered with a ring of absorbing material to reduce reflections.
ばく露装置の詳細 Twenty-four ventilated polycarbonate cages having the shape of a truncated wedge (17 to 8.5 cm wide, 35 cm long, and 15 cm high), each containing an unrestrained rat, were placed symmetrically in the chamber with their wider end near the absorbing material. A tuneable monopole antenna at the center generated a radial plane wave. The EF was vertical (perpendicular to the plates) and the MF was circumferential, parallel to the plates.
Sham exposure A sham exposure was conducted.
Additional information Four groups of 72 animals each were treated as follows: cage control, MX + sham exposure, MX + 0.3 W/kg, and MX + 0.9 W/kg. The three chambers of each exposure group were always in different racks and at different rack levels.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 0.3 W/kg mean 測定値および計算値 whole body 0.07-0.65 W/kg
SAR 0.9 W/kg mean 測定値および計算値 whole body 0.21-1.9 W/kg
Additional parameter details

The background ELF MF was below 0.1 µT, the static MF was 40-47 µT in the animal room. The stray RF fields at a distance of 0.15 m from the exposure chamber were 1 W/m² or lower, and far below 0.1 W/m² at a distance of 1 m.

測定および計算の詳細

Forward and reflected powers at the input of the exposure chambers were measured with RF power meters. The whole-body average SARs for rats in the center of the cage with their noses pointing at the center of the chamber were determined based on 1) analytical calculations with homogeneous prolate spheroidal rat models and on 2) calorimetric measurements using homogeneous rat phantoms consisting of plastic flasks filled with liquid simulating muscle, and were 3) confirmed by FDTD calculations [Puranen et al., submitted]. The resulting SARs decreased linearly with increasing rat mass from 100 g to 320 g and varied with different horizontal positions. For small rats (<110 g), the highest SAR may have been 1.2 W/kg for the low-level exposure and 3.6 W/kg for the high-level exposure if the rat was standing in an upright position.

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:
  • ばく露前
  • ばく露中
  • ばく露後

研究の主なアウトカム（著者による）

Radiofrequency irradiation did not statistically significantly affect mortality or organ-specific incidence of any tumor type.
The only statistically significant difference was an increase in the merged vascular tumors of the mesenteric lymph nodes in the "high radiofrequency irradiation group" (0.9 W/kg) compared to the "sham exposure group". However, additional histopathological analysis of the cage control animals suggested that this difference was due to unusually low number of this type of tumor in the "sham exposure group" rather than a high number in the "high radiofrequency exposure group".
With respect to non-neoplastic findings, statistically significant differences between the "radiofrequency irradiation groups" and the "sham exposure group" were found only for single findings in the lacrimal glands, lungs, liver and skin. Such changes are commonly seen in aged rats and were considered to be unrelated to radiofrequency exposure.
The data do not support cocarcinogenic effects of low-level long-term radiofrequency exposure in rats.

研究の種別:

研究助成

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