Study type: Medical/biological study (experimental study)

Membrane potential and currents of isolated heart muscle cells exposed to pulsed radio frequency fields med./bio.

By: Linz KW, von Westphalen C, Streckert J, Hansen V, Meyer R
Published in: Bioelectromagnetics 1999; 20 (8): 497-511
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Aim of study (acc. to author)

To check whether the fields transmitted from GSM-phones (900 and 1800 MHz) and other communication devices like police radio equipment (180 MHz) are able to influence the electrical characteristics of excitable cells (whether the L-type Ca2+-current can be influenced by the presence of these fields).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 1,800 MHz
Modulation type: pulsed
Exposure duration: continuous for 2 min
  • power: 1.8 W peak value (0.2, 1.2 and 1.8 W for guinea-pig cells)
  • SAR: 720 mW/kg average over time (unspecified) (80, 480 and 720 mW/kg for guinea-pig cells)
  • power: 2.2 W peak value (1.5, 1.8 and 2.2 W for rat cells)
  • SAR: 880 mW/kg average over time (unspecified) (600, 720 and 880 mW/kg for rat cells)
Exposure 2: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 2 min
  • SAR: 250 mW/kg average over time (unspecified)
Exposure 3: 900 MHz
Modulation type: pulsed
Exposure duration: continuous for 2 min
  • SAR: 15 mW/kg average over time (unspecified)
Exposure 4: 180 MHz
Modulation type: CW
Exposure duration: continuous for 2 min
  • SAR: 80 mW/kg average over time (unspecified)

General information

Isolated ventricular myocytes from guinea-pig were exposed to RF fields of 1800 MHz, 900 MHz, and 180 MHz and rat ventricular myocytes to RF fields of 1800 MHz. An experiment consisted of six phases, each one lasting about two minutes: control, exposure, control, control, sham exposure, control. Exposure and sham exposure were exchanged alternately. Usually all six phases were carried out on the same cell. If this was not possible, two cells from the same animal, each one measured in three phases, were paired.

Exposure 1

Main characteristics
Frequency 1,800 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 2 min
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 12.5 %
Repetition frequency 217 Hz
Pulse type rectangular
Additional info

GSM-standard
Exposure setup
Exposure source
  • waveguide
  • 50 cm long, 12 cm wide and 3 cm high
Chamber The experimental setup consisting of standard patch-clamp electrophysiology-equipment and an RF exposure system was mounted on a shock-absorbing platform in a Faraday cage. The RF exposure system consisted of a signal generator and an exposure device containing the chamber with the cell suspension. Depending on the frequencies applied, two different signal generators and three different exposure devices, i.e. a TEM-cell and two different rectangular waveguides, were used. The waveguides were designed for single-mode operation of the H10-mode. The coaxial line to waveguide transitions were geometry-optimized for suitable matching and low VSWR. The waveguides and the adaptors were made of brass.
Setup The specimen was kept in a constantly perfused temperature-controlled experimental chamber. The round experimental chamber, which was filled with 200 µl of cell suspension, was made of acrylic (inner diameter 10 mm, height 6 mm), and its bottom consisted of a glass coverslip to allow visual control of the cells by an inverted microscope. The outer shape of the chamber holder varied to fit the different exposure devices. All three exposure devices had an aperture in the centre of the bottom plate covered by copper meshes, above which the glass bottom of the experimental chamber was placed. Light and the patch-clamp electrode entered the exposure devices via an opening (diameter 10 mm) in the top plate of the device and an additional hole in the septum of the TEM-cell.
Additional info Temperature in the presence and the absence of the RF field was checked in separate experiments during which a temperature sensing device was introduced into the chamber. Experiments were carried out at 36 and 24 °C.
Parameters
Measurand Value Type Method Mass Remarks
power 1.8 W peak value - - 0.2, 1.2 and 1.8 W for guinea-pig cells
SAR 720 mW/kg average over time calculated unspecified 80, 480 and 720 mW/kg for guinea-pig cells
power 2.2 W peak value - - 1.5, 1.8 and 2.2 W for rat cells
SAR 880 mW/kg average over time calculated unspecified 600, 720 and 880 mW/kg for rat cells
Measurement and calculation details

Since direct measurement of the field was impossible for electrical and physiological reasons, an indirect evaluation using computer simulations starting from the field in the empty exposure device had to be performed. The test setup in the environment of the experimental chamber with the cell suspension was modelled and calculated by an in-house FDTD simulation tool based on XFDTD. The electrical material parameters (permittivity and conductivity) which could not be taken from the literature were measured with an RF network analyzer at 900 and 1800 MHz. Field homogeneity analysis showed that on the top side of the glass cover slip where the measured cells were located the field appeared very uniform. The computed electrical field strength on the axes of the empty rectangular waveguide (763 V/m) and at the location of the cells (54 V/m) as well as the SAR (3.19 W/kg) for an input power of 1 W CW were determined. From these values the actually applied time-averaged SAR as a function of the peak power of the square-modulated RF signal was calculated.

Exposure 2

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 2 min
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 12.5 %
Repetition frequency 217 Hz
Pulse type rectangular
Additional info

GSM-standard. The spectral width of the carrier signal was 3.6 kHz.
Exposure setup
Exposure source
  • waveguide
  • 50 cm long, 21 cm wide and 3 cm high
Parameters
Measurand Value Type Method Mass Remarks
SAR 250 mW/kg average over time calculated unspecified -
Measurement and calculation details

The computed electrical field strength on the axes of the empty rectangular waveguide (627 V/m) and at the location of the cells (42 V/m) as well as the SAR (1.66 W/kg) for an input power of 1 W CW were determined. From these values the actually applied time-averaged SAR as a function of the peak power of the square-modulated RF signal was calculated.

Exposure 3

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 2 min
Modulation
Modulation type pulsed
Rise time 2.5 µs
Fall time 2.5 µs
Duty cycle 12.5 %
Repetition frequency 217 Hz
Pulse type rectangular
Additional info

GSM-standard. The spectral width of the carrier signal was 3.6 kHz.
Exposure setup
Exposure source
Chamber Design of the TEM-cell and experimental setup have been described in detail in the reference article.
Parameters
Measurand Value Type Method Mass Remarks
SAR 15 mW/kg average over time calculated unspecified -

Exposure 4

Main characteristics
Frequency 180 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 2 min
Modulation
Modulation type CW
Additional info

CW was used to simulate the German police communication standard working with FM.
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 80 mW/kg average over time calculated unspecified -

Reference articles

  • Wolke S et al. (1996): Calcium homeostasis of isolated heart muscle cells exposed to pulsed high-frequency electromagnetic fields

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

The results demonstrate that the investigated radiofrequency fields do not interfere with a number of electrical membrane parameters, like resting membrane potential and action potential.

Study character:

Study funded by

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