Medical/biological study (experimental study)

Gene expression in the mammary gland tissue of female Fischer 344 and Lewis rats after magnetic field exposure (50 Hz, 100 muT) for 2 weeks med./bio.

By: Fedrowitz M, Loscher W

Published in: Int J Radiat Biol 2012; 88 (5): 425-429

Aim of study (acc. to author)

To elucidate magnetic field effect-associated candidate genes, gene expression in magnetic field-susceptible Fischer 344 rats and magnetic field-insensitive Lewis rats was compared (to explain the different strain sensitivity to magnetic field exposure as shown in a previous studies: Fedrowitz and Löscher 2008 and Fedrowitz and Löscher 2005).

Background/further details

Five rats per group at an age of 52 days were exposed and five rats per group were sham exposed (in total n=20). A total of four arrays were performed with the pooled RNA of sham exposed or exposed Fischer 344 rats and Lewis rats.

Endpoint

molecular biosynthesis: gene expression in mammary gland tissue

Exposure

- 50 Hz
- 50/60 Hz
- magnetic field
- low frequency

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: continuous for 7 days/week during 2 weeks	magnetic flux density: 100 µT effective value

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Polarization	linear
Exposure duration	continuous for 7 days/week during 2 weeks

Exposure setup

Exposure source	coil(s)
Setup	rats were exposed in their cages (5 rats per cage) located in the exposure chambers to a horizontally polarized magnetic field
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	100 µT	effective value	measured	-	-

Additional parameter details

stray field from the coils for sham exposure: B = 0.1 µT measured and calculated

Reference articles

Fedrowitz M et al. (2005): Power frequency magnetic fields increase cell proliferation in the mammary gland of female Fischer 344 rats but not various other rat strains or substrains
Fedrowitz M et al. (2002): Magnetic field exposure increases cell proliferation but does not affect melatonin levels in the mammary gland of female Sprague Dawley rats

Exposed system:

animal
rat/Fischer 344 and Lewis
whole body

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: gene expression in mammary gland tissue (microarray (Affymetrix Rat Genome 230 2.0))
body weigth (once per week)

Investigated system:

DNA/RNA

Investigated organ system:

mammary gland

Time of investigation:

during exposure
after exposure

Main outcome of study (acc. to author)

The analysis of gene expression in the mammary gland tissue revealed that altogether only 23 transcripts out of 31,100 probe sets were altered after magnetic field exposure. In the breast tissue of Lewis rats, nine genes were upregulated, whereas eight upregulations and six downregulations of gene expressions were apparent in magnetic field exposed Fischer 344 rats.
A remarkably decreased alpha-amylase gene expression, downregulations in carbonic anhydrase 6 and lactoperoxidase (both relevant for pH regulation), and an upregulated gene expression of cystatin E/M (a tumor suppressor) were found in exposed Fischer 344 rats, but not in Lewis rats.
In conclusion, the magnetic field exposed breast tissue of Fischer 344 rats showed alterations in gene expression, which were absent in Lewis rats and may therefore be involved in the magnetic field-susceptibility of Fischer 344 rats. Alpha-amylase might serve as a promising target to study magnetic field effects.

Study character:

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

Study funded by

Deutsche Forschungsgemeinschaft (DFG; German Research Foundation)

Zhao G et al. (2014): Relationship between exposure to extremely low-frequency electromagnetic fields and breast cancer risk: a meta-analysis
Chen Q et al. (2013): A Meta-Analysis on the Relationship between Exposure to ELF-EMFs and the Risk of Female Breast Cancer
Fedrowitz M et al. (2012): Effects of 50 Hz magnetic field exposure on the stress marker alpha-amylase in the rat mammary gland
Chen C et al. (2010): Extremely low-frequency electromagnetic fields exposure and female breast cancer risk: a meta-analysis based on 24,338 cases and 60,628 controls
Fedrowitz M et al. (2008): Exposure of Fischer 344 rats to a weak power frequency magnetic field facilitates mammary tumorigenesis in the DMBA model of breast cancer
Girgert R et al. (2008): Electromagnetic fields alter the expression of estrogen receptor cofactors in breast cancer cells
Feychting M et al. (2006): Electromagnetic fields and female breast cancer
Fedrowitz M et al. (2005): Power frequency magnetic fields increase cell proliferation in the mammary gland of female Fischer 344 rats but not various other rat strains or substrains
Fedrowitz M et al. (2004): Significant differences in the effects of magnetic field exposure on 7,12-dimethylbenz(a)anthracene-induced mammary carcinogenesis in two substrains of Sprague-Dawley rats
Fedrowitz M et al. (2002): Magnetic field exposure increases cell proliferation but does not affect melatonin levels in the mammary gland of female Sprague Dawley rats
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Anderson LE et al. (1999): Effect of 13 week magnetic field exposures on DMBA-initiated mammary gland carcinomas in female Sprague-Dawley rats
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Loscher W et al. (1994): Animal studies on the role of 50/60-Hertz magnetic fields in carcinogenesis