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

[未熟および若いラットのBBBに対して1439 MHz電磁ばく露の影響は見られない] med./bio.

Lack of effects of 1439 MHz electromagnetic near field exposure on the blood-brain barrier in immature and young rats

著者: Kuribayashi M, Wang J, Fujiwara O, Doi Y, Nabae K, Tamano S, Ogiso T, Asamoto M, Shirai T
掲載誌: Bioelectromagnetics 2005; 26 (7): 578-588
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この研究は、1439 MHz電磁界（EMF）の近傍界ばく露を頭部に受けたラットで、血液脳関門（BBB）への影響を調べた。実験には、未成熟ラット（4週齢：BBBの発達が完了する時期に当たる）および若齢ラット（10週齢）を用いた。頭部へのEMFの局所ばく露は、SARが0、2、および6 Wで、90分/日、1または2週間継続した。ばく露終了後に、p-糖タンパク質、アクアポリン-4、およびクローディン-5をコードする遺伝子など、BBB関連遺伝子の変化を脳のタンパク質およびmRNAレベルで評価した。陽性対照とした1,3-ジニトロベンゼン（DNB）処理群では、この3つの遺伝子の発現は明らかに減少した。結果として、対照群に比べ、いずれの年齢のラットでも、またいずれのばく露レベルでも、EMFばく露群においてこの３つの遺伝子の発現に病理学的に重要な違いはなかった；FITC-デキストラン、FD20の移行を参照に用いてモニターした血管透過性は、EMFばく露の影響を受けなかった；これらの知見は、1439 MHz EMFの頭部局所ばく露が未熟ラットおよび若齢ラットのBBBに悪影響を及ぼさないことを示す、と報告している。

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研究目的（著者による）

To study whether electromagnetic field exposure causes any damage of blood-brain barrier in rats with ages equivalent to the time of blood-brain barrier genesis and the young adult.

詳細情報

Immature (4 weeks old) and young (10 weeks old) rats were used.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 1,439 MHz
Modulation type: pulsed
ばく露時間: repeated daily exposure, 90 min/day, 6 days/week, for 1 or 2 weeks
  • SAR: 2 W/kg average over mass (brain)
  • SAR: 6 W/kg average over mass (brain)
  • SAR: 0.29 W/kg maximum (whole body)

ばく露1

主たる特性
周波数 1,439 MHz
タイプ
  • electromagnetic field
特性
  • near field
ばく露時間 repeated daily exposure, 90 min/day, 6 days/week, for 1 or 2 weeks
Additional information Wang J, Fujiwara O. 2004. A new method for realizing local exposure to young rat heads using electric flux concentration for bio-effect test of mobile telephones. Proceedings of the International Symposium on Electromagnetic Compatibility, Sendai, June 2004:581-584.
Modulation
Modulation type pulsed
Duty cycle 33 %
Repetition frequency 50 Hz
Additional information

TDMA signal for the PDC (Japanese cellular telephone standard) system
ばく露装置
ばく露の発生源／構造
  • モノポール
  • 1/4 wavelength
Distance between exposed object and exposure source 3 cm
チャンバの詳細 The exposure box (90 x 90 x 60 cm) was made of metal, and its walls were inlaid with pyramidal EM wave absorber, except for the metal roof, which formed the ground of the antenna installed vertically in its center [Shirai et al., 2005]. A disk-like plate was supported by a central hollow cylinder pole through which air was ventilated into the box.
ばく露装置の詳細 Rats were individually fixed in plastic holders and were set on the disk-shaped plate like a carrousel with their noses pointing to the central antenna at a distance of 3 cm. A flexible ferroelectric sheet, 1 mm thick, covering the head part of the plastic holder concentrated the electric flux in a circle which resulted in a strong magnetic field in the region of the rat head.
Sham exposure A sham exposure was conducted.
Additional information Ten exposure boxes were placed in a shielded room, and 10 rats were exposed at the same time with the same SAR. After one week, five rats in each group were sacrificed and replaced by live dummy rats (not used in any analysis) to maintain the exposure condition.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 2 W/kg average over mass 測定値および計算値 brain -
SAR 6 W/kg average over mass 測定値および計算値 brain -
SAR 0.29 W/kg maximum 測定値および計算値 whole body -
測定および計算の詳細

SAR distribution in the brain and whole body of rats was determined numerically using the FDTD method with anatomically based rat models with a voxel size of 1 mm and 17 tissue types and was validated by measurements on a homogeneous gel phantom using an infrared image camera and fluor-optic temperature probes. The calculated and measured results were in good agreement [Wang and Fujiwara, 2004].

Reference articles

  • Shirai T et al. (2005): [携帯電話用1.439 GHz電磁界への慢性ばく露はF344ラットのENU誘発中枢神経系腫瘍をプロモートしない]

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）

Although expression of the three genes was decreased after administration of 1,3-dinitrobenzene as a positive control, when compared with the control values, there were no pathologically relevant differences with the electromagnetic field at any exposure levels at either age. Vascular permeability, measured with reference to transfer of FITC-dextran, was not affected by electromagnetic field exposure.
Thus, these data indicate that local exposure of the head to 1439 MHz electromagnetic field exerts no adverse effects on the blood-brain barrier in immature and young rats.

研究の種別:

研究助成

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