この研究は、マウスの脳において、超低周波磁界ばく露強度（50 Hz；ばく露レベル0、0.1、0.2、1、2 mT；1日15時間で7日間連続ばく露）と熱ショックタンパク（hsp70）発現およびDNA損傷に量‐反応関係があるか否かを調べた。成獣雄CD1マウスを合計96匹用いた。擬似ばく露群（32匹）、4つのばく露レベル群（各16匹）のそれぞれの半数はばく露終了直後に、残りの半数は24時間後に、それぞれ線条体、海馬、小脳のHsp70発現およびDNA損傷を調べた。その結果、hsp70のmRNA とその対応タンパク質の両方に、ばく露による変化は何も見られなかったが、例外として、0.1 mTにおいて海馬のmRNAのみが若干上昇した；1および2 mTにばく露し、ばく露の直後に調べた場合にのみ、対照群に比較して脳の3つの領域の標本でのDNA鎖切断が高まった；24時間後に調べた場合、このようなDNA鎖切断はベースラインまで回復していた、と報告している。
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8 groups of mice were exposed to 4 different magnetic flux densities (2 groups for every flux density). Each group consisted of 4 subgroups: 1.) directly killed after exposure (n=4), 2.) 24 hours killed after exposure (n=4), 3.) directly killed after sham exposure (n=2) and 4.) 24 hours killed after sham exposure (n=2).
The positive control for the protein expression of Hsp70 was performed via an increased environmental temperature until rectal temperature reached 42°C and as a positive control for the DNA damage, mice were radiated with x-rays (6 Gy).
No differences were observed among the groups regarding food intake and body weight gain.
Between the groups, no changes were found in the expression of Hsp70 (mRNA and protein). Only in the hippocampus of 0.1 mT exposed mice, a weak, but significant increase in the expression of the hsp70 mRNA was found in comparison to sham exposed animals.
Directly after exposure to magnetic flux densities of 1 and 2 mT, a significant increase regarding DNA damage was found compared to sham exposed mice. However, 24 hours after the exposure, the DNA damage recovered and no significant differences between the exposed and the sham exposed mice were found.
The authors conclude, that exposure to extremely low frequency magnetic fields may lead to reversible DNA damage in the brain of mice, but does not affect Hsp70 expression.