Medical/biological study (experimental study)

Evaluation of rat thyroid gland morphophysiological status after three months exposure to 50 Hz electromagnetic field med./bio.

By: Rajkovic V, Matavulj M, Gledic D, Lazetic B

Published in: Tissue Cell 2003; 35 (3): 223-231

Aim of study (acc. to author)

To study the effects of an extremely low frequency electromagnetic field on rat thyroid gland.

Background/further details

A total of 89 animals were used. The exposure group consisted of 47 and the control group of 42 animals. To investigate in vivo recovery periode of thyroid gland the animals were divided into four groups differing in the time point of sacrifice after exposure: group 1) sacrificed the day after exposure, group 2) sacrificed one week, group 3) two weeks and group 4) sacrificed three weeks after electromagnetic field exposure.

Endpoint

morphol./histopathol. changes: morphological changes in thyroid gland
endocrine changes: concentration of thyroid gland hormones

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: repeated daily exposure, 7 h/day, 5 days/week for 3 months	electric field strength: 10 V/m magnetic flux density: 50 µT minimum (on the opposite side of the coils) magnetic flux density: 500 µT maximum (at the coils)

General information

47 animals were exposed, 42 served as control.

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Exposure duration	repeated daily exposure, 7 h/day, 5 days/week for 3 months

Exposure setup

Exposure source	coil(s)
Setup	Animals were placed in cages which were placed symmetrically on both sides of the coil.
Additional info	Control animals were maintained in a seperate room free of any appliances involved in generation.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
electric field strength	10 V/m	-	measured	-	-
magnetic flux density	50 µT	minimum	unspecified	-	on the opposite side of the coils
magnetic flux density	500 µT	maximum	unspecified	-	at the coils

Additional parameter details

The coils produced EMF of decaying intensity along the cages with a 500 µT on the side of the cage near the coil and 50 µT on the opposite side.

Exposed system:

animal
rat/Mill Hill
whole body

Methods Endpoint/measurement parameters/methodology

morphol./histopathol. changes: morphological changes in thyroid gland (e.g. volume densities of thyroid follicles, follicular epithelium, colloid, capillary network; hematoxylin-eosin stain and PAS alcian blue staining, light microscopy)
endocrine changes: triiodothyronine (T3), thyroxine (T4) concentrations (radioimmunoassay)

Investigated system:

isolated bio./chem. substance
tissue slices
blood

Investigated organ system:

Time of investigation:

after exposure

Main outcome of study (acc. to author)

Histological analyses showed that the volume density of follicular epithelium and thyroid activation index (ratio of the volume density of follicular epithelium to the volume density of colloid) decreased, while the volume density of colloid and capillary network increased in group 1, 2 and 3. However, the values of all these parameters in group 4 were similar to corresponding control group.
Serum T3 and T4 concentrations were significantly lower in exposed animals of group 2-4 compared to control group.
Results demonstrate that after significant morphophysiological changes caused by extremely low frequency electromagnetic field exposure thyroid gland recovered morphologically, but not physiologically (hormone level), during the investigated recovery period.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministry of Science and Technology, Serbia

Rajkovic V et al. (2010): Studies on the synergistic effects of extremely low-frequency magnetic fields and the endocrine-disrupting compound atrazine on the thyroid gland
Anselmo CW et al. (2009): Effects of the electromagnetic field, 60 Hz, 3 microT, on the hormonal and metabolic regulation of undernourished pregnant rats
Burchard JF et al. (2006): Plasma concentrations of thyroxine in dairy cows exposed to 60 Hz electric and magnetic fields
Rajkovic V et al. (2006): Light and electron microscopic study of the thyroid gland in rats exposed to power-frequency electromagnetic fields
Rajkovic V et al. (2005): Stereological analysis of thyroid mast cells in rats after exposure to extremely low frequency electromagnetic field and the following "off" field period
Rajkovic V et al. (2005): Histological characteristics of cutaneous and thyroid mast cell populations in male rats exposed to power-frequency electromagnetic fields
Rajkovic V et al. (2005): The effect of extremely low-frequency electromagnetic fields on skin and thyroid amine- and peptide-containing cells in rats: an immunohistochemical and morphometrical study
Rajkovic V et al. (2001): Morphophysiological status of rat thyroid gland after subchronic exposure to low frequency electromagnetic field
Matavulj M et al. (2000): Studies on the possible endocrinological effects of a 50 Hz electromagnetic field
Lafreniere GF et al. (1979): Thyroid morphology and activity does not respond to ELF electromagnetic field exposures
Ossenkopp KP et al. (1972): Prenatal exposure to an extremely low frequency-low intensity rotating magnetic field and increases in thyroid and testicle weight in rats