Sun Wenjun, Gan Yaping, Fu Yiti, Lu Deqiang, Chiang Huai
Bioelectromagnetics Laboratory, 2Institute of Environmental Medicine, School of Medicine, Zhejiang University, Hangzhou, China.
Cell Physiol Biochem. 2008;22(5-6):507-14. doi: 10.1159/000185524. Epub 2008 Dec 9.
Previously, we found that exposure to a 50-Hz magnetic field (MF) at 0.4 mT could induce epidermal growth factor (EGF) receptor clustering in Chinese hamster lung (CHL) fibroblast cells and superposition of an incoherent MF with the same intensity could inhibit the effect. In the present experiment, we investigated the effects of 50-Hz MF exposure at different intensities on EGF receptor clustering and phosphorylation in human amniotic cells (FL), and explored the interaction effect of an incoherent MF. Clustering and phosphorylation of EGF receptors on cellular membrane surface were analyzed using immunofluorescence assessed by confocal microscopy and western blot technology, respectively. EGF treatment served as a positive control. The results showed that, compared with sham exposure, exposure to a 50-Hz MF at 0.1, 0.2 or 0.4 mT for 15 min could significantly induce EGF receptor clustering and enhance phosphorylation on tyrosine-1173 residue in FL cells, whereas exposure to a 0.05 mT field for 15 min did not caused a significant effect. Exposure to an incoherent MF (frequency range between 30 to 90 Hz) at 0.2 mT for the same time neither induced EGF receptor clustering nor enhanced phosphorylation of EGF receptor in FL cells. When superposed, the incoherent MF at 0.2 mT completely inhibited EGF receptor clustering and phosphorylation induced by a 50-Hz MF at 0.1 and 0.2 mT. However, the incoherent MF could not completely eliminate the effects induced by a 0.4 mT 50-Hz MF. Based on the results of this experiment, we conclude that membrane receptors could be one of the main targets where extremely-low frequency (ELF) MF interacts with cells, and the intensity threshold, in the case of EGF receptors, is between 0.05 and 0.1 mT. An incoherent MF could completely inhibit the effects induced by an ELF-MF of equal or lower intensity.
此前，我们发现，中国仓鼠肺（CHL）成纤维细胞暴露于0.4 mT的50 Hz磁场（MF）中可诱导表皮生长因子（EGF）受体聚集，叠加相同强度的非相干MF可抑制该效应。在本实验中，我们研究了不同强度的50 Hz MF暴露对人羊膜细胞（FL）中EGF受体聚集和磷酸化的影响，并探讨了非相干MF的相互作用效应。分别使用共聚焦显微镜评估的免疫荧光和蛋白质印迹技术分析细胞膜表面EGF受体的聚集和磷酸化。EGF处理作为阳性对照。结果表明，与假暴露相比，FL细胞暴露于0.1、0.2或0.4 mT的50 Hz MF中15分钟可显著诱导EGF受体聚集并增强酪氨酸-1173残基的磷酸化，而暴露于0.05 mT磁场中15分钟则未产生显著影响。同时暴露于0.2 mT的非相干MF（频率范围在30至90 Hz之间）既未诱导FL细胞中EGF受体聚集，也未增强EGF受体的磷酸化。当叠加时，0.2 mT的非相干MF完全抑制了0.1和0.2 mT的50 Hz MF诱导的EGF受体聚集和磷酸化。然而，非相干MF不能完全消除0.4 mT的50 Hz MF诱导的效应。基于本实验结果，我们得出结论，膜受体可能是极低频（ELF）MF与细胞相互作用的主要靶点之一，就EGF受体而言，强度阈值在0.05至0.1 mT之间。非相干MF可完全抑制强度相等或更低的ELF-MF诱导的效应。
