Study type: Medical/biological study (experimental study)

Calcium homeostasis of isolated heart muscle cells exposed to pulsed high-frequency electromagnetic fields med./bio.

By: Wolke S, Neibig U, Elsner R, Gollnick F, Meyer R
Published in: Bioelectromagnetics 1996; 17 (2): 144-153
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Aim of study (acc. to author)

To investigate possible non-thermal effects of GSM exposure characteristics on intracellular calcium homeostasis in isolated cardiac muscle cells of guinea pigs.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 900 MHz
Modulation type: CW
Exposure duration: continuous for 500 s
  • SAR: 59 mW/kg mean (also peak value)
Exposure 2: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 500 s
Exposure 3: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 500 s
Exposure 4: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 500 s
Exposure 5: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 500 s
Exposure 6: 1,300 MHz
Modulation type: pulsed
Exposure duration: continuous for 500 s
Exposure 7: 1,800 MHz
Modulation type: pulsed
Exposure duration: continuous for 500 s
Exposure 8: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 120 min

General information

The experimental schedule varied carrier frequency (900, 1300, and 1800 MHz), modulation frequency (0, 16, 50, 217 Hz, and 30 kHz at 900 MHz), and membrane potential. The experiments included sham runs with the same handling and duration.

Exposure 1

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 500 s
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber The TEM cell was mounted on the object stage of the inverted microscope and contained an open 10-mm experimental chamber for holding the sample. The bottom of this chamber consisted of a glass coverslip and a 1-mm mesh made of 0.05-mm wire and provided shielding while allowing optical observation.
Setup The sample volume (200 µl of cell suspension) in the Plexiglas chamber was maintained at 37 ± 0.5 °C by perfusion of the preheated solution and an additional heating fluid running through a circular channel around the sample volume.
Sham exposure A sham exposure was conducted.
Additional info An experimental run consisted of three phases each lasting 500 s. The first phase without any exposure was followed by field exposure. During the third phase a chemical stimulation (K+-depolarization) was performed indicating the viability of the cells which served as positive control.
Parameters
Measurand Value Type Method Mass Remarks
SAR 59 mW/kg mean measured and calculated - also peak value
Measurement and calculation details

The SAR values achieved were determined by combined measurements and calculations. Field distribution and SAR for 1 W were calculated first. Then the input power to the TEM cell was measured for each applied signal using a bolometer. Finally, the actual SAR values were obtained by multiplication. The SAR values calculated on this basis were only spatial mean values within the solution. The metal mesh, however, created local field inhomogeneities at the level of the cells since the field lines converged towards the wires of the mesh. Calculations on this showed that local SAR values varied by one order of magnitude (or a factor of 3) depending on the position of an individual cell. One millimeter above the wire mesh, the field distribution was even.

Exposure 2

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 500 s
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 50 %
Repetition frequency 16 Hz
Pulse type rectangular
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 29 mW/kg mean measured and calculated - -
SAR 57 mW/kg peak value measured and calculated - -

Exposure 3

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 500 s
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 50 %
Repetition frequency 50 Hz
Pulse type rectangular
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 30 mW/kg mean measured and calculated - -
SAR 59 mW/kg peak value measured and calculated - -

Exposure 4

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 500 s
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 14 %
Repetition frequency 217 Hz
Pulse type rectangular
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Additional info In one set of experiments, the membrane potential of the cells was adjusted to different values (-80 mV, -50, -30, and 0 mV). In the third phase, the membrane potential of the depolarized cells was repolarized to -80 mV. This set also included sham runs at each membrane potential.
Parameters
Measurand Value Type Method Mass Remarks
SAR 15 mW/kg mean measured and calculated - -
SAR 123 mW/kg peak value measured and calculated - -

Exposure 5

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 500 s
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 80 %
Repetition frequency 30 kHz
Pulse type rectangular
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 37 mW/kg mean measured and calculated - -
SAR 47 mW/kg peak value measured and calculated - -

Exposure 6

Main characteristics
Frequency 1,300 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 500 s
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 14 %
Repetition frequency 217 Hz
Pulse type rectangular
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 12 mW/kg mean measured and calculated - -
SAR 99 mW/kg peak value measured and calculated - -

Exposure 7

Main characteristics
Frequency 1,800 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 500 s
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 14 %
Repetition frequency 217 Hz
Pulse type rectangular
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 9 mW/kg mean measured and calculated - -
SAR 69 mW/kg peak value measured and calculated - -

Exposure 8

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 120 min
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 14 %
Repetition frequency 217 Hz
Pulse type rectangular
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Additional info In a third set of experiments, long-term exposures were tested. The first phase (without field) lasted 5 min and was followed by 120 min of exposure and 25 min of chemical stimulation (positive control).
Parameters
Measurand Value Type Method Mass Remarks
SAR 15 mW/kg mean measured and calculated - -
SAR 123 mW/kg peak value measured and calculated - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

No significant differences between sham exposure and high-frequency field exposure were found, exept one very small in the case of the 900 MHz (50Hz modutation) exposure. According to the results of this study an influence of pulsed high-frequency fields at GSM range on the intracellular calcium level in isolated cardiac muscle cells is not entirely excluded. However, such influences are very unlikely.

Study character:

Study funded by

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