Medical/biological study (experimental study)

Melatonin and N-tert-butyl-alpha-phenylnitrone block 60-Hz magnetic field-induced DNA single and double strand breaks in rat brain cells med./bio.

By: Lai H, Singh NP

Published in: J Pineal Res 1997; 22 (3): 152-162

Aim of study (acc. to author)

To study whether treatment with melatonin and N-tert-butyl-alpha-phenylnitrone (PBN) could block the genotoxic effect of magnetic fields on brain cell DNA.

Background/further details

In previous studies the authors have found an increase in DNA single-strand breaks and double-strand breaks in brain cells of rats after acute exposure to a sinusoidal 60-Hz magnetic field (see publication 2063).
Rats were injected with melatonin (1 mg/kg) or PBN (100 mg/kg) immediately before and after two hours of exposure.

Endpoint

genotoxicity/mutation: DNA damage (single-strand breaks; double-strand breaks)

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 60 Hz Exposure duration: 2 h	magnetic flux density: 140 nT (ambient MF) magnetic flux density: 0.5 mT unspecified (unspecified)

Exposure 1

Main characteristics

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

Exposure setup

Exposure source	Helmholtz coils two sets, each with 40 turns wound in rectangular loops, 0.86 m x 0.543 m
Chamber	plastic cage with styroform cover (45 cm long x 21 cm wide x 22 cm high)
Setup	two seperate rooms with two similar exposure systems; the cage placed in the center of the space between the coils
Additional info	Helmholtz coil arranged in such a way that it could be switched "in phase" to generate MF or in "bucking mode" to cancel the fields generated by each other. Bucking mode was used as control to determine the effects of heat and vibration.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	140 nT	-	measured	-	ambient MF
magnetic flux density	0.5 mT	unspecified	measured	unspecified	-

Measurement and calculation details

The magnetic field was measured with an EMDEX 2 meter.

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 damage (single-strand breaks; double-strand breaks; microgel electrophoresis assay (length of DNA migration))

Investigated system:

DNA/RNA
cell lysates

Investigated organ system:

brain/CNS

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The data confirmed previous findings that acute exposure to a 60 Hz magnetic field increases DNA single-strand breaks and double-strand breaks in rat brain cells.
Both drug treatments blocked the magnetic field-induced DNA single-strand breaks and double-strand breaks in brain cells. Since melatonin and PBN are efficient free radical scavengers, these findings suggest that free radicals may play a role in magnetic field-induced DNA damage.

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

Korr H et al. (2014): No evidence of persisting unrepaired nuclear DNA single strand breaks in distinct types of cells in the brain, kidney, and liver of adult mice after continuous eight-week 50 Hz magnetic field exposure with flux density of 0.1 mT or 1.0 mT
Villarini M et al. (2013): Brain hsp70 expression and DNA damage in mice exposed to extremely low frequency magnetic fields: a dose-response study
Rageh MM et al. (2012): Assessment of genotoxic and cytotoxic hazards in brain and bone marrow cells of newborn rats exposed to extremely low-frequency magnetic field
Belyaev IY et al. (2009): Microwaves from UMTS/GSM mobile phones induce long-lasting inhibition of 53BP1/gamma-H2AX DNA repair foci in human lymphocytes
Koyama S et al. (2008): Extremely low frequency (ELF) magnetic fields enhance chemically induced formation of apurinic/apyrimidinic (AP) sites in A172 cells
Udroiu I et al. (2006): Clastogenicity and aneuploidy in newborn and adult mice exposed to 50 Hz magnetic fields
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
Koyama S et al. (2004): ELF electromagnetic fields increase hydrogen peroxide (H2O2)-induced mutations in pTN89 plasmids
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
Singh N et al. (1998): 60 Hz magnetic field exposure induces DNA crosslinks in rat brain cells
Lai H et al. (1997): Melatonin and a spin-trap compound block radiofrequency electromagnetic radiation-induced DNA 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