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Medical/biological study (experimental study)

Characterization of the suppressive effects of extremely-low-frequency electric fields on a stress-induced increase in the plasma glucocorticoid level in mice.

Published in: Bioelectromagnetics 2018 [in press]

Aim of study (acc. to author)

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.
Background/further details: 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).

Endpoint

Exposure

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
Exposure 1
Main characteristics
Frequency 50 Hz
Type
Exposure duration continuously for 60 minutes
Additional info groups 2 and 5a) - g)
Exposure setup
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
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 10 kV/m - measured - ± 1%
magnetic flux density 0.12 nT - measured - ± 4 nT
Measurement and calculation details
EF strength was measured at 273 arbitrary points (21 x 13) on each cage floor
Exposure 2
Main characteristics
Frequency 60 Hz
Type
Exposure duration continuously for 60 minutes
Additional info groups 3 and 6
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 10 kV/m - measured - ± 1%
magnetic flux density 0.12 nT - measured - ± 4 nT
Measurement and calculation details
electric field strength was measured at 273 arbitrary points (21 x 13) on each cage floor
Reference articles
Exposed system:
  • animal
  • mouse/BALB/c
  • whole body

Methods Endpoint/measurement parameters/methodology

Investigated material:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

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.
Study character:

Study funded by

  • not stated/no funding

Related articles

  • Di G et al. (2018): A comparative study on effects of static electric field and power frequency electric field on hematology in mice.
  • Harakawa S et al. (2017): Time-dependent changes in the suppressive effect of electric field exposure on immobilization-induced plasma glucocorticoid increase in mice.
  • Hori T et al. (2017): Configuration-dependent variability of the effect of an electric field on the plasma glucocorticoid level in immobilized mice.
  • Hori T et al. (2015): Exposure to 50 Hz electric fields reduces stress-induced glucocorticoid levels in BALB/c mice in a kV/m- and duration-dependent manner.
  • Szemerszky R et al. (2010): Stress-related endocrinological and psychopathological effects of short- and long-term 50Hz electromagnetic field exposure in rats.
  • Harakawa S et al. (2004): Effect of a 50 Hz electric field on plasma ACTH, glucose, lactate, and pyruvate levels in stressed rats.
  • de Bruyn L et al. (1994): Electric field exposure and evidence of stress in mice.
  • Margonato V et al. (1993): Biologic effects of prolonged exposure to ELF electromagnetic fields in rats. I. 50 Hz electric fields.
  • Free MJ et al. (1981): Endocrinological effects of strong 60-Hz electric fields on rats.
  • Hackman RM et al. (1981): Corticosterone levels in mice exposed to high-intensity electric fields.