The effects of co-exposure of mice to a 50 or 60 Hz electric field and illuminance as well as field shielding on the immobilization stress-induced increase in blood glucocorticoid level should be investigated.
In previous studies, the authors reported that an immobilization stress-induced increase in glucocorticoid level in mice was suppressed by exposure to a 50 Hz electric fields (Hori et al. 2015, Hori et al. 2017).
Mice were divided into the following groups (n=6-8 each): 1) control group, 2) exposure to 50 Hz EF alone, 3) exposure to 60 Hz EF alone, 4) immobilization stress alone, 5) exposure to 50 Hz EF and immobilization stress, 6) exposure to 60 Hz EF and immobilization stress. Furthermore, conditions from groups 1), 2), 4) and 5) were combined with a) high (490 lux), b) moderate (200 lux) and c) low (0 lux) illumination, resulting in further groups 1a), 1b), 1c) - 5a), 5b), 5c). Lastly, conditions from group 5 were additionally combined with EF shielding, by wrapping mice restrainers in electrically conductive foil with sheet width d) 5 mm, e) 20 mm and f) 80 mm for partial shielding and g) 200 mm for complete shielding, resulting in groups 5d) - 5g).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuously for 60 minutes
groups 2 and 5a) - g)
|
|
|
Exposure 2:
60 Hz
Exposure duration:
continuously for 60 minutes
groups 3 and 6
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | continuously for 60 minutes |
| Additional info | groups 2 and 5a) - g) |
| Exposure source | |
|---|---|
| Chamber | cylindrical plastic cage (diameter: 200 mm; height: 100 mm) with slits (length: 100 mm; width: 5 mm) all around at 5-mm intervals to prefent smudges |
| Setup | parallel plate electrode system was comprised of two stainless-steel electrodes (1,000 x 600 mm) placed over and under the cage; humidity was maintained between 45% and 55%; the temperature inside the cage was 25°C ± 3°C during EF or sham exposure |
| Sham exposure | A sham exposure was conducted. |
| Additional info | immobilization stress was induced by immobilizing each mouse separately within a 50 ml centrifuge (polypropylene) tube that was placed on the lower electrode; immobilization was applied during the latter half (30 min) of the 60-min EF test period in respective groups |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 10 kV/m | - | measured | - | ± 1% |
| magnetic flux density | 0.12 nT | - | measured | - | ± 4 nT |
| Frequency | 60 Hz |
|---|---|
| Type | |
| Exposure duration | continuously for 60 minutes |
| Additional info | groups 3 and 6 |
| Exposure source |
|
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 10 kV/m | - | measured | - | ± 1% |
| magnetic flux density | 0.12 nT | - | measured | - | ± 4 nT |
There was no significant difference in the plasma glucocorticoid levels between mice exposed to a 50 Hz (group 2) or 60 Hz (group 3) EF and the control group. However, glucocorticoid levels in mice exposed to immobilization stress alone (group 4) were significantly higher than those in control mice. Glucocorticoid levels in groups with immobilization and EF exposure (groups 5 and 6) were also significantly higher than those in control mice but significantly lower than in group 4.
Red blood cell count, hemoglobin level and hematocrit were significantly lower in the control group than in groups 2-6. There was no significant difference in any blood parameter between groups 4, 5 and 6.
In all illuminance conditions, there were no significant differences in glucocorticoid levels between the EF exposure alone groups (groups 2a, b and c) and the control group, and immobilization alone (groups 4a, b, c) resulted in significantly higher values than in the control group. Only at 200 lux, the glucocorticoid level in the co-treatment group (group 5b) was significantly lower than without EF exposure (group 4b).
Glucocorticoid levels in the co-treated but shielded animals (groups 5d - g) were significantly higher than those in the control mice, but in groups 5d) and 5e) (5 and 20 mm sheet width, respectively) the levels were significantly lower than those in the group 4 and a significant negative correlation between the effect of EF and the area shielded was found.
The authors conclude that illuminance and the size of the exposed body area might influence the suppressive effects of an 50 Hz or 60 Hz electric field on immobilization stress-induced increase in plasma glucocorticoid levels.
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