To investigate the effects of extremely low frequency magnetic fields on human T-type calcium channels transfected in embryonic kidney cells and on native T-type calcium channels in cultured mouse cortical neurons.
T-type calcium channels are low-voltage activated calcium channels. They play key roles in various physiological and pathological functions.
The T-type calcium channels Cav3.1, Cav3.2 and Cav3.3 were transfected in human embryonic kidney cells.
The primary cultured cortical neurons were used to test whether magnetic field exposure inhibits native T-type channel currents via a leukotriene E4 pathway.
Leukotriene E4 is produced by the oxidation of arachidonic acid and involved in inflammation processes.
Experiments were partially performed with the inhibitors CAY10502 (inhibits the release of arachidonic acid), BAYµ9773 (leukotriene receptor antagonist) or bestatin (blocks the conversion from leukotrien D4 to leukotrien E4).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuously for up to 3 hours (0.5 h, 1 h, 2 h, 3 h)
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform |
|
| Exposure duration | continuously for up to 3 hours (0.5 h, 1 h, 2 h, 3 h) |
| Exposure source | |
|---|---|
| Setup | magnetic field was produced by a pair of Helmholtz coils, powered by an AC generator system; exposure did not change the temperature of the CO2 incubator (37 °C) |
| Sham exposure | A sham exposure was conducted. |
| Additional info | sham exosed control group was placed in the same incubator but without magnetic field |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 200 µT | unspecified | measured | - | - |
In exposed cell cultures of embryonic kidney cells, the cell currents were significantly decreased after 0.5 and 1 hour exposure compared to the control group. That means that the T-type channels (Cav3.1, Cav3.2 and Cav3.3) were inhibited. The inhibitor CAY10502 and bestatin abrogated the exposure-related inhibitory effect. To further verify the results, leukotriene E4 was added to the culture medium, which mimicked the exposure-related inhibition of calcium channels. However, neither the expression of the T-type channel Cav3.2 nor the steady-state activation and inactivation kinetics were changed by exposure. Arachidonic acid and leukotriene E4 were significantly increased after 0.5 and 1 hour exposure in comparison to the control group.
In primary cultured mouse cortical neurons, the exposure significantly inhibited the T-type channel currents when compared to the control group. Experiments with the inhibitor bestatin and addition of leukotriene E4 indicated that the inhibition is mediated via a leukotriene E4 pathway.
The authors conclude that extremely low frequency magnetic fields inhibit T-type calcium channels in transfected embryonic kidney cells and primary cultured cortical neurons through an arachidonic acid and leukotriene E4 dependent pathway.
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