Study type: Medical/biological study (experimental study)

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. med./bio.

Published in: Cancer Res 2004; 64 (1): 243-251

Aim of study (acc. to author)

To compare different substrains of Sprague-Dawley rats in respect to magnetic field effects on cell proliferation in the mammary gland, susceptibility to DMBA-induced mammary cancer, and magnetic field effects on mammary tumor development and growth in the DMBA model.

Background/further details

The authors suggest that genetic differences between substrains of Sprague-Dawley rats are involved in different results of different groups/laboratories on mammary tumor development (q.v. publication 4796). The Sprague-Dawley substrain SD1 was considered magnetic field sensitive and used for comparison with other substrains.
Rats of DMBA experiments received the first application of DMBA (5 mg/rat) at the first day of magnetic field or sham exposure. Rats were administered 20 mg DMBA in four weekly doses.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: repeated daily exposure, 24 h/day, 7 days a week for 18 weeks
Exposure 2: 50 Hz
Exposure duration: repeated daily exposure, 24 h/day, 7 days a week for 2 weeks

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Exposure duration repeated daily exposure, 24 h/day, 7 days a week for 18 weeks
Additional info horizontally polarized magnetic field
Exposure setup
Exposure source
Chamber Three exposure chambers with room for four cages were used for exposure. Three identical but non-energized exposure chambers were located at the other side of the same room for sham exposure.
Additional info Both exposed and sham control rats were administered with 4 weekly doses of 5 mg/rat DMBA (7,12-dimethylbenz(a)anthracene) in sesame oil.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 100 µT effective value measured - -

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Exposure duration repeated daily exposure, 24 h/day, 7 days a week for 2 weeks
Additional info horizontally polarized magnetic field
Exposure setup
Exposure source
Additional info In the morning of the last day of exposure, all the rats received an 50 mg/kg i.p injection of BrdUrd (bromodeoxyuridine).
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 100 µT effective value measured - -

Reference articles

  • Mevissen M et al. (1998): Acceleration of mammary tumorigenesis by exposure of 7,12-dimethylbenz[a]anthracene-treated female rats in a 50-Hz, 100-microT magnetic field: replication study.
  • Baum A et al. (1995): A histopathological study on alterations in DMBA-induced mammary carcinogenesis in rats with 50 Hz, 100 muT magnetic field exposure.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
  • breast
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

In contrast with SD1 rats, no enhanced cell proliferation was found after magnetic field exposure in SD2 rats. Magnetic field exposure significantly increased mammary tumor development and growth in SD1 but not in SD2 rats.
These findings indicate that the genetic background plays an important role in effects of magnetic field exposure. Different strains or substrains of rats may serve to evaluate the genetic factors underlying sensitivity to cocarcinogenic or tumor-promoting effects of magnetic field exposure.

Study character:

Study funded by

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