Study type: Medical/biological study (experimental study)

Effect of the Light Regime and Electromagnetic Fields on Carcinogenesis of the Mammary Gland in Female Rats. med./bio.

Published in: Biophysics 1996; 41 (4): 817-823

Aim of study (acc. to author)

To investigate the effects of electromagnetic fields in combination with different lighting regimes on tumor development in femal rats. Mammary carcinoma (i.e. adenocarcinoma) were induced by intravenously administration of the chemical carcinogen N-nitrosomethylurea (NMU). Furthermore, blood levels of melatonin and prolactin were determined.

Background/further details

Two different experiments were conducted.
Experiment 1) Animals were exposed to three different ligthing regimes (i.e. normal leighting 12 h lightness/12 h darkness; 24 h darkness; or 24 h leightness). After two weeks of acclimatization to the ligthing regims the animals recived the chemical carcinogen NMU in a dose of 50 mg/kg three times at weekly intervals. Magnetic field exposure (either varying or constant) was started from the second day after the first NMU-injection. Animals were exposed for 3 h/day for 15 months. However, blood samples were taken after 4 weeks of MF-exposure to determine melatonin and prolactin levels.
Experiment 2) Animals were kept under a normal light regim (12 h light/12 h dark). A part of the animals were blinded by enucleation of both eyeballs. Two weeks thereafter animals recived a single NMU dose (50 mg/kg). Rats were dissected and histologically examined for tumor classification.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: 3 h/day for up to 15 months
Exposure 2:
Exposure duration: 3 h/day for up to 15 months

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration 3 h/day for up to 15 months
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic field strength 160 A/m - measured - -

Exposure 2

Main characteristics
Frequency
Type
Exposure duration 3 h/day for up to 15 months
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic field strength 300 A/m - measured - -

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Normal light regime combined with a varying magnetic field leads to a sooner adenocarcinoma development as compared with control groups. However, carcinogenesis was much more stimulated by constant illumination, whereas constant dark inhibited carcinogenesis. Constant illumination leads to an decreased level of melatonin and an increased level of prolactin. Blinded rats exhibited fewer mammary adenocarcinoma and showed an increased expection of life than sighted rats.

Study character:

Study funded by

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