Medical/biological study (experimental study)

60 Hz magnetic field exposure induces DNA crosslinks in rat brain cells med./bio.

By: Singh N, Lai H

Published in: Mutation Research - Fundamental and Molecular Mechanism of Mutagenesis 1998; 400 (1-2): 313-320

Aim of study (acc. to author)

To study whether exposure to a 60 Hz magnetic field causes DNA-protein and DNA-DNA crosslinks in brain cells of the rat.

Background/further details

To study DNA-protein crosslinks, the slides in the microgel electrophoresis assay were treated with proteinase-K before electrophoresis which removes the protein from the DNA.
DNA is negatively charged and moves to the anode during electrophoresis. Most proteins crosslinked to DNA are positively charged and move to the cathode (thus, removal of protein would free the DNA and results in an increased DNA migration).
Some slides were additionally irradiated with X-rays (to identify DNA-DNA crosslinks).
The authors also compared the effects of magnetic fields with those of a known crosslink inducing agent (mitomycin C) (these experiment were performed in human lymphocytes).

Endpoint

genotoxicity/mutation: DNA-DNA and DNA-protein crosslinks, DNA strand breaks

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: 2 h	magnetic flux density: 500 µT unspecified power: 8 W maximum (at 1 mT exposure)

Exposure 1

Main characteristics

Frequency	60 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	2 h

Exposure setup

Exposure source	Helmholtz coils
Chamber	Plastic cage/ 45 cm x 21 cm wide x 22 cm high
Setup	coils wound on frames fabricated from wood and aluminium; cage was placed in the center of the space between the coils

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	500 µT	unspecified	measured	-	-
power	8 W	maximum	-	-	at 1 mT exposure

Additional parameter details

Ambient MF at the laboratory was 0.14 µT.

Reference articles

Lai H et al. (1993): Effects of a 60 Hz magnetic field on central cholinergic systems of the rat

Exposed system:

Methods Endpoint/measurement parameters/methodology

genotoxicity/mutation: DNA-DNA and DNA-protein crosslinks, DNA strand breaks (microgel electrophoresis)

Investigated system:

DNA/RNA
cell lysates

Investigated organ system:

brain/CNS

Time of investigation:

after exposure

Main outcome of study (acc. to author)

These data indicate that both DNA-protein and DNA-DNA crosslinks are formed in brain cells of rats after acute exposure to a 60 Hz magnetic field. This is shown by the findings that magnetic field-induced DNA migration was only revealed after proteinase-K digestion, magnetic field exposure impeded X-ray-induced migration and proteinase-K treatment did not further increase X-ray-induced migration. This is further supported by the similarity to the effects of mitomycin C on lymphocyte DNA.

Study character:

medical/biological study
experimental study
full/main study
blind study

Study funded by

National Institute of Environmental Health Sciences (NIEHS), North Carolina, USA

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Villarini M et al. (2013): Brain hsp70 expression and DNA damage in mice exposed to extremely low frequency magnetic fields: a dose-response study
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Yokus B et al. (2008): Extremely low frequency magnetic fields cause oxidative DNA damage in rats
McNamee JP et al. (2005): Evaluating DNA damage in rodent brain after acute 60 Hz magnetic-field exposure
Lai H et al. (2004): Magnetic-field-induced DNA strand breaks in brain cells of the rat
McNamee JP et al. (2002): DNA damage and apoptosis in the immature mouse cerebellum after acute exposure to a 1 mT, 60 Hz magnetic field
Svedenstal BM et al. (1999): DNA damage induced in brain cells of CBA mice exposed to magnetic fields
Svedenstal BM et al. (1999): DNA damage, cell kinetics and ODC activities studied in CBA mice exposed to electromagnetic fields generated by transmission lines
Lai H et al. (1997): Melatonin and N-tert-butyl-alpha-phenylnitrone block 60-Hz magnetic field-induced DNA single and double strand breaks in rat brain cells
Lai H et al. (1997): Acute exposure to a 60 Hz magnetic field increases DNA strand breaks in rat brain cells