この研究は、マウスの線維芽細胞L929を用い、低レベルの無線周波（RF）電磁界ばく露および温度上昇が、オルニチンデカルボキシラーゼ（ODC）活性に及ぼす影響を調べた。ばく露に用いた900MHz RFは、パルス変調波（パルス周波数217 Hz、GSMタイプの変調）または連続波のどちらかで、SARレベルは0.2 W/ kg（0.1-0.3 W/ kg）および0.4 W/ kg（0.3-0.5 W/ kg）、ばく露時間は2、8、または24時間とした。その結果、RFばく露は細胞ODC活性に影響を与えなかった；ただし、ばく露システムにおける温度のわずかな上昇（0.8〜0.9℃）が、培養細胞におけるODC活性低下をもたらした；これは、細胞をインキュベーター内で異なる温度にさらす試験により検証された；ODC活性は細胞培養における小さな温度差に敏感であることが示されたので、細胞ODC活性の研究においては正確な温度制御が必要である、と報告している。
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To study the effects of low-level radiofrequency irradiation and elevated temperature (< 1°C) on ornithine decarboxylase activity in murine fibroblasts.
Changing of culture medium and 50 Hz sine wave magnetic field (10 µT) were used as positive controls.
|Repetition frequency||217 Hz|
|チャンバの詳細||The waveguide exposure chamber was an aluminium RF resonator with a plastic cultivation chamber and a water circulation heat exchanger for keeping the temperature of the cell culture medium constant (± 0.3°C). The water circulated under a glass surface on which the cell-culture dishes were placed. Glass Petri dishes were used instead of plastic dishes for better thermal contact. There were two identical chambers, one for exposure and one for sham-exposure. However, the temperature of the water circulation heat exchanger in the exposure chamber (37.5 ± 0.3°C) was found to be, on average, 0.8°C higher than in the sham exposure chamber (36.7 ± 0.3°C), despite the temperature control. Warm air (approx. 37°C) and CO2 (5%) were fed into the cultivation chambers from a cell culture incubator.|
|ばく露装置の詳細||The RF power source consisted of a signal generator, a 217 Hz GSM modulator, and power amplifier. RF power was fed into the exposure chamber with a monopole post, and the electric field inside the chamber, below the heat exchanger, was monitored from another monopole post with an RF power meter.|
|Additional information||Two Petri dishes were exposed simultaneously, and two dishes were sham-exposed. This was repeated 3-5 times at each exposure level and duration. In separate additional experiments, cells were incubated in ordinary cell culture incubators for 2 h at 37.6°C and 36.5°C measured with a Fluke thermometer and thermocouple in the medium. Magnetic fields were measured in both incubators to be 1.1 µT at 50 Hz at the position of the cell dishes. Cells were handled exactly in the same way as in the exposures in the waveguide system.|
Radiofrequency irradiation did not affect cellular ornithine decarboxylase activity. However, a slight increase in temperature (0.8-0.9°C) in the exposure system resulted in decreased ornithine decarboxylase activity in cell cultures. This was verified by tests in which cells were exposed to different temperatures in incubators (37.6°C and 36.5°C).
The data showed that ornithine decarboxylase activity is sensitive to small temperature differences in cell cultures.