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Medical/biological study (experimental study)

Brain hsp70 expression and DNA damage in mice exposed to extremely low frequency magnetic fields: a dose-response study.

Published in: Int J Radiat Biol 2013; 89 (7): 562-570

Aim of study (acc. to author)

To evaluate whether there is a dose-response relationship between exposure to extremely low frequency magnetic fields at different magnetic flux densities and the protein expression of the heat shock protein Hsp70 and DNA damage in the brain of mice.
Background/further details: 8 groups of mice were exposed to 4 different magnetic flux densities (2 groups for every flux density). Each group consisted of 4 subgroups: 1.) directly killed after exposure (n=4), 2.) 24 hours killed after exposure (n=4), 3.) directly killed after sham exposure (n=2) and 4.) 24 hours killed after sham exposure (n=2).
The positive control for the protein expression of Hsp70 was performed via an increased environmental temperature until rectal temperature reached 42°C and as a positive control for the DNA damage, mice were radiated with x-rays (6 Gy).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: 15 hours/day for 7 days
Exposure 2: 50 Hz
Exposure duration: 15 hours/day for 7 days
Exposure 3: 50 Hz
Exposure duration: 15 hours/day for 7 days
Exposure 4: 50 Hz
Exposure duration: 15 hours/day for 7 days
Exposure 1
Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration 15 hours/day for 7 days
Exposure setup
Exposure source
Chamber mice were exposed in a plastic cage in the centre of the apparatus
Setup rectangular coils arranged horizontally in a Helmholtz-like configuration, apparatus placed in a temperature-controlled room (22±1°C)
Sham exposure A sham exposure was conducted.
Additional info during sham exposure the magnetic flux density was 0.06 µT
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.1 mT effective value - - -
Additional parameter details
during sham exposure, magnetic flux density was 0.06 µT
Exposure 2
Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration 15 hours/day for 7 days
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.2 mT effective value - - -
Exposure 3
Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration 15 hours/day for 7 days
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT effective value - - -
Exposure 4
Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration 15 hours/day for 7 days
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT effective value - - -
Reference articles
  • Mariucci G et al. (2010): Brain DNA damage and 70-kDa heat shock protein expression in CD1 mice exposed to extremely low frequency magnetic fields.
Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated material:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

No differences were observed among the groups regarding food intake and body weight gain.
Between the groups, no changes were found in the expression of Hsp70 (mRNA and protein). Only in the hippocampus of 0.1 mT exposed mice, a weak, but significant increase in the expression of the hsp70 mRNA was found in comparison to sham exposed animals.
Directly after exposure to magnetic flux densities of 1 and 2 mT, a significant increase regarding DNA damage was found compared to sham exposed mice. However, 24 hours after the exposure, the DNA damage recovered and no significant differences between the exposed and the sham exposed mice were found.
The authors conclude, that exposure to extremely low frequency magnetic fields may lead to reversible DNA damage in the brain of mice, but does not affect Hsp70 expression.
Study character:

Study funded by

  • Fondazione Cassa di Risparmio di Perugia, Italy
  • University of Perugia, Italy

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