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

[連続波または50 Hz変調無線周波数放射へのばく露後のL929細胞のオルニチンデカルボキシラーゼ活性―再現研究] med./bio.

Ornithine decarboxylase activity of L929 cells after exposure to continuous wave or 50 Hz modulated radiofrequency radiation--a replication study

著者: Höytö A, Juutilainen J, Naarala J
掲載誌: Bioelectromagnetics 2007; 28 (7): 501-508
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以前の研究で報告された無線周波数(RF)電磁界ばく露後のげっ歯類L929線維芽細胞におけるオルニチンデカルボキシラーゼ(ODC)活性増強を確認するために、やや範囲を広げた再現研究が行われた。2つの細胞バンクから購入されたL929細胞は、2.5W/kgまたは6.0W/kgの比吸収率(SAR)レベルの、連続波またはDAMPS（50Hz変調バースト、デューティサイクル33％）信号に、2、8、24時間ばく露された。ばく露はクロフォード・セルチャンバーと導波管チャンバーで、周波数はそれぞれ835MHzと872MHzで行われた。この結果では、これまでの研究が報告しているRFにばく露された細胞におけるODC活性の上昇を確認することはできなかった。クロフォードばく露システムでは、ODC活性は影響を受けないか(8時間または24時間ばく露において)、または最高レベルSAR(6W/kg)の2時間ばく露後に低下した。活性低下は気流冷却装置が使用されなかった場合に最も多く表れ、おそらく温度上昇に関連している。小さな方法論的違い(抗生物質の使用、ODC分析の感度上昇)が、今回と以前の研究における知見の相違を説明することはないであろう。より効率的な温度制御を組み入れた導波管システムを使用した実験では違った知見が得られた。このばく露システムでは、ODC活性は6W/kgでの8時間ばく露後に上昇した。今後の研究では、この知見が本当の非熱効果を反映したものかどうか探求することが必要である。今回の研究は、先行研究で報告された変調に特異的な影響についての証拠は提供していない。

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研究目的（著者による）

A replication study with some extensions was made to confirm enhancement of ornithine decarboxylase enzyme activity in murine L929 fibroblasts after radiofrequency electromagnetic field exposure reported in earlier studies (publication 1718 and publication 3382).

詳細情報

L929 cells purchased from two cell banks were exposed for 2, 8, or 24 h to continuous wave or D-AMPS signal. In positive control experiments, medium change was used to induce and serum deprivation to suppress ornithine decarboxylase activity.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 835 MHz
Modulation type: CW
ばく露時間: continuous for 2, 8, or 24 h
ばく露2: 835 MHz
Modulation type: pulsed
ばく露時間: continuous for 2, 8, or 24 h
ばく露3: 872 MHz
Modulation type: pulsed
ばく露時間: continuous for 8 h

General information

RF and sham exposures were carried out in Crawford chambers and in waveguide exposure chambers. In sham-sham experiments, cell flasks or dishes were placed in both exposure chambers, and no RF field was applied.

ばく露1

主たる特性
周波数 835 MHz
タイプ
  • electromagnetic field
特性
  • guided field
ばく露時間 continuous for 2, 8, or 24 h
Modulation
Modulation type CW
ばく露装置
ばく露の発生源／構造
チャンバの詳細 The Crawford chambers were housed in a water jacketed CO2 incubator. Compared to the design used by Penafiel et al. [1997], a few modifications were made to improve the setup: The doors were enlarged, shelves were added inside, power sensors were fitted, and ventilators were introduced. These improvements increased the accuracy and reproducibility of exposures.
ばく露装置の詳細 Cells seeded into two sealed 25 cm² plastic flasks were placed in each of the two chambers, one for RF and one for sham exposure.
Sham exposure A sham exposure was conducted.
Additional information The air flow was on to cool the exposed cells, except for a series of experiments performed without air cooling at 6.0 W/kg. The computerised setup enabled performing experiments in a blinded manner.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 2.5 W/kg - - - -
SAR 6 W/kg - - - -
測定および計算の詳細

The description of dosimetry was published elsewhere [Nikoloski et al., 2005].

ばく露2

主たる特性
周波数 835 MHz
タイプ
  • electromagnetic field
特性
  • guided field
ばく露時間 continuous for 2, 8, or 24 h
Modulation
Modulation type pulsed
Duty cycle 33.3 %
Repetition frequency 50 Hz
Additional information

D-AMPS modulated signal
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 2.5 W/kg - - - -
SAR 6 W/kg - - - -

ばく露3

主たる特性
周波数 872 MHz
タイプ
  • electromagnetic field
特性
  • guided field
ばく露時間 continuous for 8 h
Modulation
Modulation type pulsed
Duty cycle 33.3 %
Repetition frequency 50 Hz
Additional information

modulation similar to that used in the D-AMPS system
ばく露装置
ばく露の発生源／構造
チャンバの詳細 The waveguide exposure system described previously [Hoyto et al., 2006] provided a uniform SAR distribution (±35%) in cell cultures, and a water cooling system enabled exposure in controlled temperature (±0.3°C).
ばく露装置の詳細 Cells plated in two 55-mm glass Petri dishes were placed in each of the two chambers, one for RF and one for sham exposure.
Sham exposure A sham exposure was conducted.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 6 W/kg - - - -

Reference articles

  • Höytö A et al. (2006): [適度の温度上昇はL929細胞のODC活性に影響する：低レベルのラジオ周波数では影響は見られない]
  • Nikoloski N et al. (2005): [再現実験用のTEMセルIn vitroばく露装置の再評価と改良]
  • Penafiel LM et al. (1997): [L929細胞でのオルニチン脱炭酸酵素活性に対するマイクロ波の影響における変調の果たす役割]

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）

The study did not confirm previous data reporting increased ornithine decarboxylase enzyme activity. When an exposure system was used similar to that of previous studies (Crawford cell), ornithine decarboxylase activity was either not affected (8 or 24 h exposures) or decreased (after a 2 h exposure at 6 W/kg). The decrease was statistically significant only for L929 cells purchased from ATCC cell bank and most pronounced when cooling with air flow was not used.
Different results were found in experiments with another exposure system with more efficient temperature control: ornithine decarboxylase activity was increased after 8 h of exposure at 6 W/kg when the temperatures of exposed cultures and control groups were kept identical (statistically significant for D-AMPS signal). Further studies are warranted to explore whether this finding reflect a true non-thermal effect.
The present study did not provide evidence for modulation-specific effects (no difference between CW- and D-AMPS signals in any of the experiments).

研究の種別:

研究助成

Replicated studies

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