To evaluate the early effects of acute exposure (2 h) to extremely low frequency electromagnetic fields, as well as movement restraint (to induce psychological and physical stress) and the combination of both on the antioxidant systems in the plasma, liver, kidney, and heart of rats.
Cells can be protected against stress by exposing them first to a brief dose of the same or different stress (e.g. heat, chemicals, brief ischemia or electromagnetic field exposures). The authors tested the hypothesis that a brief exposure to extremely low frequency electromagnetic fields could induce adaptive changes on the antioxidant systems, particularly in those tissues with high oxidative metabolism like the liver, kidney and heart. This pre-conditioning could lead to protective effects against oxidative stress.
24 male rats were divided in two groups: restrained and unrestrained. The restrained animals were confined into an acrylic tube for 120 min. Half of the animals of each group (n=6) were exposed to extremely low frequency electromagnetic fields during the period of immobilization.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
60 Hz
Exposure duration:
continuous for 2 hr
|
|
animals were divided into four groups: i) in movement restrained ii) in movement restrained + exposure to EMF iii) in movement unrestrained + exposure to EMF iv) control - no restrainment + no exposure
| Frequency | 60 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 2 hr |
| Exposure source | |
|---|---|
| Setup | rats were restrained by confinement into a 18 cm long acrylic cylinder with an inner diameter of 7 cm; unrestained rats were placed in 47 cm x 25 cm x 21 cm acrylic cages; pair of circular Helmholtz coils with an inner diameter of 30 cm, consisting of 350 turns of 18-gauge copper wire, separated by 15 cm; coils lying on the upper and lower cage surfaces |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 2.4 mT | - | measured | - | - |
Glutathione concentration was significantly lower in the heart of all experimental animals when compared to the control group (i.e. no exposure, unrestraint); furthermore, the decrease was higher in the liver of both restrained groups (i.e. strongest decrease). Superoxide dismutase enzyme activity was lower in the plasma of all restrained and electromagnetic field exposed animals compared to the unrestrained and non-exposed control rats. There were no significant differences in catalase enzyme activity and thiobarbituric acid reactive substances levels among all the experimental groups vs. the control group.
The authors conclude that two hours of 60 Hz exposure might immediately alter the metabolism of free radicals, decreasing superoxide dismutase activity in plasma and glutathione content in heart and kidney, but does not induce immediate lipid peroxidation. Oxidative stress induced by movement restraint was stronger than that produced by electromagnetic field exposure.
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