Study type: Medical/biological study (experimental study)

Exposure of DMBA-treated female rats in a 50-Hz, 50 microTesla magnetic field: effects on mammary tumor growth, melatonin levels, and T lymphocyte activation. med./bio.

Published in: Carcinogenesis 1996; 17 (5): 903-910

Aim of study (acc. to author)

To investigate the effects of a magnetic field (MF) exposure on mammary tumor growth, melatonin levels, and proliferation capacity of spleenic T lymphocytes in rats.

Background/further details

Mammary tumors were induced by the use of the chemical carcinogen DMBA. The first DMBA application (5mg/rat) at the onset of exposure was followed by three more applications at weekly intervals up to a total of 20 mg DMBA/rat.
A total of 216 animals were used in this study, divided into four groups. Group A) 99 animals, DMBA treated, MF exposed. Group B) 99 animals DMBA treated, sham-exposed. Group C) 9 animals, non DMBA treated, MF exposed. Group D) 9 animals, non DMBA treated, sham-exposed.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Modulation type: CW
Exposure duration: continuous, 24 h/day, 7days/week, for 91 days

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous, 24 h/day, 7days/week, for 91 days
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber exposure chambers, 4 cages 39x55x22cm, 9-10 animals/cage
Setup cages inside the coils
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 50 µT - measured - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

8 weeks after DMBA application, significantly more tumors were found in the MF-exposed group than in sham-exposed animals. At time of autopsy, significantly more MF-exposed DMBA-treated animals exhibited macroscopically visible mammary tumors than DMBA-treated controls.
Proliferation of spleenic T lymphocytes was determined at the end of exposure time and revealed a significant suppression in MF exposed non DMBA treated animals compared with MF sham-exposed non DMBA treated rats.
No signifficant difference was seen in nocturnal melatonin levels of DMBA-treated MF exposed and sham-exposed animals. (determination after 9 and 12 weeks after onset of exposure.)
Other findings: No behavioural differences were observed between exposed and sham-exposed animals. Furthermore, no significant differences were found for body weight, spleen, and liver weight were among the four groups.
The results of this study indicates that long-term 50 µT MF exposure of DMBA-treated female rats significantly enhances mammary tumor development and growth.

Study character:

Study funded by

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