To study the combined effects of exposure to an extremely low frequency magnetic field and various stress factors including ionizing radiation, hydrogen peroxide, and oncogenic c-Myc activation on cellular transformation in non-tumorigenic NIH3T3 cells.
NIH3T3 cells were used because NIH3T3 cells showed sensitive transforming activity even in the weaker carcinogens.
For the positive control, cells were exposed to various doses of gamma radiation (0, 0.5, 1, 2, and 4 Gy as a single or fractionated dose) at a dose rate of 3.81 Gy/min. For H2O2 exposure, cells were treated with H2O2 (0, 50, 100, 150, and 200 mM) for 4 h.
For the co-exposure experiments, there were three conditions: 1) cells exposed to an extremely low frequency magnetic field for 4 h, 2) cells exposed to an extremely low frequency magnetic field (1 mT) for 4 h immediately after irradiation with gamma rays (2 Gy), and 3) cells exposed to an extremely low frequency magnetic field (1 mT) for 4 h in the presence of H2O2 (100 µM).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
60 Hz
Exposure duration:
continuous for 4 h
|
|
Cells were treated in six groups: i) sham exposure ii) EMF exposure with 0.01, 0.5, 1 mT iii) ionizing gamma radiation iv) EMF exposure with 1 mT immediately after gamma radiation v) exposure to H2O2 vi) EMF exposure with 1 mT in the presence of H2O2
| Frequency | 60 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for 4 h |
| Exposure source |
|
|---|---|
| Setup | four square coils arranged on a 270 mm x 200 mm support forming a rectangular tower with three exposure layers: bottom, middle and top layer; inner coils with 11 turns, bottom and top coils with 26 turns; exposure system shielded with ferrite material and placed inside a CO2 incubator with a constant temperature of 37°C ±0.2°C; cells placed in 60 mm Petri dishes on the bottom, middle and top layer |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 0.01 mT | - | measured | - | - |
| magnetic flux density | 0.5 mT | - | measured | - | - |
| magnetic flux density | 1 mT | - | measured | - | - |
A 4 h exposure of NIH3T3 cells to extremely low frequency magnetic field alone produced no cell transformation. Moreover, extremely low frequency magnetic field exposure did not influence the transformation activity of ionizing radiation, hydrogen peroxide, or activated c-Myc in this in vitro assay, suggesting that 1 mT extremely low frequency magnetic field did not affect any additive or synergistic transformation activities in combination with stress factors such as ionizing radiation, hydrogen peroxide, or activated c-Myc in NIH3T3 cells.
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