この実験研究はヒト末梢血リンパ球において、無線周波電磁界（RF）ばく露により適応応答（AR）［訳者注］が生じるか否かを調べた。9人の健常被験者から採取したリンパ球細胞をphytohaemagglutinin （PHA）添加培養液で培養した後、ADとして、異なるSAR（1.25、0.6、0.3、0.15 W/kg）のUMTS信号（1950 MHz）ばく露または擬似ばく露を与え、その後、CDとして100 ng/ml のマイトマイシン（MMC）を与えて、回収したリンパ球における小核（MN）の頻度を遺伝毒性の指標として測定した。その結果、SAR 0.3 W/kg のRFを事前にADとした与えた場合、AD無しの場合に比べてMN頻度が有意に減少したことから、RFばく露によるARが見られたと報告している。［訳者注］適応応答とは、前もって適応dose（AD）を与えると、その後に与えるチャレンジdose（CD）に対する応答が弱くなる現象。この研究では、基礎実験として、実験に使用した9検体にMMCによるARがあるか否かを、ADとして1 ng/ml のMMCを与え、CDとして100 ng/m のMMCを与えた場合の反応をAD無しの場合と比較して調べた。その一方で、ADとしてRFばく露を与えた場合について、AD無し（擬似ばく露）の場合と比較することが本研究の主目的である。
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To examine the influence of different specific absorption rates on the adaptive response induced by the exposure of human blood lymphocytes to radiofrequency fields.
Former studies have shown that different cell types exposed to an extremely small adaptation dose of a genotoxic agent are less susceptible to the induction of a genetic damage when given a higher challenge dose of the same or a similar genotoxic agent. The induction of an adaptive response was shown to be influenced by several factors (e.g. the dose used for adaptation, the dose rate, the time between the adaptation and challenge doses).
Blood lymphocytes of nine male healthy donors were stimulated for 24 h with phytohaemagglutinin and then exposed for 20 hours to an adaptive dose of 1950 MHz radiofrequency field at different specific absorption rates (1.25, 0.6,0.3 and 0.15 W/kg). This was followed by a challenge dose of 100 ng/ml mitomycin C. Cells were collected after 72 h total culture period and the frequency of micronuclei was recorded.
The lymphocytes from donors 1-3 were exposed at 1.25 and 0.3 W/kg while the lymphocytes from donors 4-6 were exposed at 0.6 and 0.15 W/kg. Whole blood samples from donors 7-9 were employed to set up cultures exposed at 1.25 and 0.3 W/kg on day 1, and at 0.6 and 0.15 W/kg on day 2.
Cells were treated in the following four groups: i) RF exposure ii) sham exposure iii) RF exposure + 100 ng/ml mitomycin C (MMC) iv) sham exposure + 100 ng/ml MMC experiment 1: lymphocytes from donors 1-3 were exposed at 1.25 and 0.3 W/kg experiment 2: lymphocytes from donors 4-6 were exposed at 0.6 and 0.15 W/kg experiment 3: blood samples from donors 7-9 were employed to set up cultures exposed at 1.25 and 0.3 W/kg on day 1, and at 0.6 and 0.15 W/kg on day 2
|ばく露時間||continuous for 20 h|
|チャンバの詳細||109.2 mm high and 54.6 mm wide WR430 rectangular short-circuited waveguide with a coaxial adapter at the feeding side|
|ばく露装置の詳細||both waveguides (for exposure and sham exposure) placed in the same incubator; in each waveguide four 35 mm Petri dishes were positioned one above the other with a 22 cm distance between the two middle dishes and a 26 distance between the middle and the outer dishes; when the centres of the samples were at a distance of 0.56 λ from the short circuit the efficiency of the exposure system was approximately 70% and the degree of non-uniformity in SAR was 0.33 in all samples.|
|Sham exposure||A sham exposure was conducted.|
In cell cultures of all nine donors, the frequencies of micronuclei in the lymphocytes exposed or sham exposed alone were not significantly different from those in untreated controls, while treatment of the cells with mitomycin C alone resulted in a significant increase compared with the untreated controls.
The results were different in different donors. According to the results between "radiofrequency field + mitomycin treatment" and the corresponding "sham exposure + mitomycin treatment", there were significant differences (decreases) at both 0.3 W/kg and 0.6 W/kg specific absorption rates. The data indicated that a radiofrequency field at 0.3 W/kg was a more reliable specific absorption rate to induce an adaptive response than a radiofrequency field at 0.6 W/kg.
Two donors did not show an adaptive response to mitomycin C nor to the radiofrequency field exposure.
The proliferation index in all cell cultures was not significantly different between untreated control lymphocytes, those exposed to "radiofrequency + mitomycin C", and those treated with mitomycin C alone.