Study type: Medical/biological study (experimental study)

Effect of pulsed electromagnetic field exposure on adenosine receptors in rat brain. med./bio.

Published in: Bioelectromagnetics 2012; 33 (4): 279-287

Aim of study (acc. to author)

To study the effects of a pulsed electromagnetic field exposure on adenosine recptors A1 and A2A in the rat cerebral cortex and cortical neurons.

Background/further details

Adenosine, an endogenous modulator of a wide range of biological functions, interacts with at least four cell surface receptor subtypes (as A1, A2A, A2B and A3 adenosine receptors). A1 and A2A adenosine receptors are highly expressed in the central nervous system compared to the other receptor subtypes.
The brain, cerebral cortex and membranes were prepared from male Sprague-Dawley rats.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 75 Hz
Modulation type: pulsed
Exposure duration: continuous for 2 h, 4 h, 6 h or 8 h
Exposure 2: 75 Hz
Modulation type: pulsed
Exposure duration: continuous for 2 h, 4 h, 6 h or 8 h

Exposure 1

Main characteristics
Frequency 75 Hz
Type
Waveform
Exposure duration continuous for 2 h, 4 h, 6 h or 8 h
Modulation
Modulation type pulsed
Pulse width 1.3 ms
Duty cycle 0.1 %
Exposure setup
Exposure source
Setup pair of rectangular horizontal coils (14 cm x 23 cm), each made of 1400 turns of copper wire placed opposite to each other; the biological samples (culture in flasks (9,2 cm x 8,2 cm with 10 ml of medium) or brain in a beaker (containing physiological oxygenated buffer)) were placed between the coils, so that the plane of the coils was perpendicular to the culture flasks
Sham exposure A sham exposure was conducted.
Additional info coils were powered by a PEMF generator system
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1.5 mT peak value measured - ± 0,2 mT (in air at the level of the biological samples)

Exposure 2

Main characteristics
Frequency 75 Hz
Type
Waveform
Exposure duration continuous for 2 h, 4 h, 6 h or 8 h
Modulation
Modulation type pulsed
Pulse width 1.3 ms
Duty cycle 0.1 %
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 3 mT peak value measured - ± 0,2 mT (in air at the level of the biological samples)

Reference articles

  • De Mattei M et al. (2009): Adenosine analogs and electromagnetic fields inhibit prostaglandin E2 release in bovine synovial fibroblasts.
  • Varani K et al. (2008): Characterization of adenosine receptors in bovine chondrocytes and fibroblast-like synoviocytes exposed to low frequency low energy pulsed electromagnetic fields.
  • Varani K et al. (2003): Alteration of A(3) adenosine receptors in human neutrophils and low frequency electromagnetic fields.
  • Varani K et al. (2002): Effect of low frequency electromagnetic fields on A2A adenosine receptors in human neutrophils.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Affinity values were not affected by pulsed electromagnetic field (PEMF) exposure, either at 1.5 or 3 mT. The PEMF exposure of the intact rat cerebral cortex or cortical neurons at 1.5 mT mediated a transient and significant increase in A2A adenosine receptors density after 4 h and 6 h of exposure and returned to values similar to controls after 8 h. In addition, PEMF exposure of the cerebral cortex and cortical neurons at 3 mT upregulated A2A adenosine receptors after 2 h and 4 h. The exposure of cortex membranes at 1.5 and 3 mT induced an increase in A2A adenosine receptor density after 2 h and was constant at all exposure times investigated.
PEMF exposure did not modify binding parameters of A1 adenosine receptors, such as affinity and density at 1.5 or 3 mT.
In cortical neurons, mRNA levels of A1 and A2A adenosine receptors were not affected by PEMF exposure for the times and intensities investigated. These results suggest that the PEMF-induced alteration of A2A adenosine receptors comprises the expression of receptors at the surface of the cell membrane, but not the transcriptional level.
In conclusion, the data clearly suggest a time and intensity-dependent effect of PEMFs on A2A adenosine receptors density in rat brain and cortical neurons. The PEMF-mediated upregulation of A2A adenosine receptors was constant in brain membranes and transient in the whole brain or intact cortical neurons.

Study character:

Study funded by

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