Wey H E, Conover D P, Mathias P, Toraason M, Lotz W G
The National Institute for Occupational Safety and Health, Cincinnati, Ohio 45226, USA.
Environ Health Perspect. 2000 Feb;108(2):135-40. doi: 10.1289/ehp.00108135.
An effect on intracellular calcium continues to be proposed as a biochemical pathway for the mediation of biologic effects of electrical-power-frequency magnetic fields (MF). However, reproducible results among laboratories are difficult to attain and the characteristics of magnetic field effects on intracellular free calcium (Ca(2+)) are not well understood. We attempted to repeat the studies of Lindström et al. [Intracellular Calcium Oscillations in a T-Cell Line by a Weak 50 Hz Magnetic Field. J Cell Physiol 156:395-398 (1993)] by investigating the effect of a 1.5-G 50-Hz MF on Ca(2+) in the Jurkat lymphocyte T-cell line. Changes in Ca(2+) were determined using microscopic imaging of fura-2 loaded Jurkat cells on poly-l-lysine-coated glass coverslips. The MF was generated by a single coil constructed with bifilar wire and located in the same plane as the cells. Cells were randomly exposed for 8 min to MF, sham field (SF), or no field (NF) conditions. The exposure condition remained coded until data analysis was complete. Each exposure period was preceded by an 8-min data collection to establish a baseline for Ca(2+). After each exposure condition, cells were exposed to anti-CD3 antibody that induced a rapid increase in Ca(2+) in responsive cells; this provided a positive control. Ca(2+) was analyzed for individual cells as spatially-averaged background-corrected 340/380 nm ratios, and a Ca(2+) transient was considered significant for positive deviations from baseline of 3 [multiple] an estimate of noise in the baseline. Typically, 25-50 cells/field were viewed and approximately 50% had no Ca(2+) transients in the baseline period and also responded to positive control. Only cells responding to positive control and lacking changes in Ca(2+) during the baseline period were considered qualified for assessment during the exposure period. The incidences of Ca(2+) transients during the exposure period for two experiments (40 [multiple] objective) were 16.5, 14.6, and 14.2% for MF, SF, and NF, respectively, and were not statistically significantly different. Previous studies by Lindström et al. [Intracellular Calcium Oscillations in a T-Cell Line after Exposure to Extremely-Low-Frequency Magnetic Fields with Variable Frequencies and Flux Densities. Bioelectromagnetics 16:41-47 (1995)] showed a high response rate (92%) for exposure to 1. 5-G 50-Hz MF when individual cells were preselected for investigation. We found no such effect when examining many cells simultaneously in a random and blind fashion. These results do not preclude an effect of MF on Ca(2+), but suggest that responsive cells, if they exist, were not identified using the approaches that we used in this study.
关于细胞内钙的影响，仍然有人提出这是工频磁场（MF）介导生物学效应的一条生化途径。然而，各实验室之间难以获得可重复的结果，而且磁场对细胞内游离钙（Ca(2+)）影响的特征尚未得到充分了解。我们试图重复林德斯特伦等人的研究[通过50 Hz弱磁场诱导T细胞系中的细胞内钙振荡。《细胞生理学杂志》156:395 - 398(1993)]，研究1.5 G 50 Hz的MF对Jurkat淋巴细胞T细胞系中Ca(2+)的影响。使用在聚-L-赖氨酸包被的玻璃盖玻片上负载fura-2的Jurkat细胞的显微镜成像来测定Ca(2+)的变化。MF由用双线绕制的单个线圈产生，并与细胞位于同一平面。细胞随机暴露于MF、假磁场（SF）或无磁场（NF）条件下8分钟。在数据分析完成之前，暴露条件一直处于编码状态。每个暴露期之前先进行8分钟的数据收集，以建立Ca(2+)的基线。在每个暴露条件之后，将细胞暴露于抗CD3抗体，该抗体可使反应性细胞中的Ca(2+)迅速增加；这提供了一个阳性对照。将Ca(2+)作为空间平均的背景校正340/380 nm比值对单个细胞进行分析，并且当Ca(2+)瞬变相对于基线的正偏差为基线噪声估计值的3倍时，认为该瞬变具有显著性。通常，每个视野观察25 - 50个细胞，大约50%的细胞在基线期没有Ca(2+)瞬变，并且对阳性对照有反应。仅将在基线期对阳性对照有反应且Ca(2+)无变化的细胞视为在暴露期有资格进行评估。在两个实验（40倍物镜）的暴露期内，MF、SF和NF条件下Ca(2+)瞬变的发生率分别为16.5%、14.6%和14.2%，差异无统计学意义。林德斯特伦等人先前的研究[暴露于具有可变频率和通量密度的极低频磁场后T细胞系中的细胞内钙振荡。《生物电磁学》16:41 - 47(1995)]表明，当预先选择单个细胞进行研究时，暴露于1.5 G 50 Hz的MF有较高的反应率（92%）。当我们以随机和盲法同时检查许多细胞时，未发现这种效应。这些结果并不排除MF对Ca(2+)有影响，但表明如果存在反应性细胞，使用我们在本研究中采用的方法无法识别它们。
