Study type: Medical/biological study (experimental study)

An investigation of the effects of TETRA RF fields on intracellular calcium in neurones and cardiac myocytes med./bio.

By: Green AC, Scott IR, Gwyther RJ, Peyman A, Chadwick P, Chen X, Alfadhl Y, Tattersall JE
Published in: Int J Radiat Biol 2005; 81 (12): 869-885
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Aim of study (acc. to author)

To determine whether Terrestrial Trunked Radio (TETRA) fields can affect intracellular calcium signalling in excitable cells.

Background/further details

Cultured rat cerebellar granule cells and cardiac myocytes were loaded with the calcium-sensitive fluorescent probes fura- PE-3, fluo-3 (granule cells), and fluo-4 (cardiac myocytes).
The TETRA communication system incorporates a pulsed modulation at 17.6 Hz, very close to the 16 Hz modulation which has been reported to enhance calcium efflux (publication 309 and publication 8142).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 380.8875 MHz
Modulation type: pulsed
Exposure duration: continuous for 20 min
  • SAR: 400 mW/kg average over mass (10 g) (320-480 mW/kg)
Exposure 2: 380.8875 MHz
Modulation type: pulsed
Exposure duration: consecutive levels for a total of 40 min
  • SAR: 5 mW/kg average over mass (10 g)
  • SAR: 10 mW/kg average over mass (10 g)
  • SAR: 20 mW/kg average over mass (10 g)
  • SAR: 50 mW/kg average over mass (10 g)
Exposure 3: 380.8875 MHz
Modulation type: pulsed
Exposure duration: continuous for 11 min
  • SAR: 400 mW/kg average over mass (10 g) (320-480 mW/kg)
  • SAR: 50 mW/kg average over mass (10 g)

Exposure 1

Main characteristics
Frequency 380.8875 MHz
Type
Exposure duration continuous for 20 min
Modulation
Modulation type pulsed
Duty cycle 25 %
Repetition frequency 17.6 Hz
Exposure setup
Exposure source
Setup Cells were exposed to TETRA RF fields in a perfusion chamber mounted on the stage of an inverted microscope within a stripline parallel-plate transmission line. The exposure system that is depicted with measures in a figure, was similar to that described in the reference article, but adapted to fit the stage of the inverted microscope. TETRA RF waveforms were provided by a function generator and an amplifier. The output waveform from the signal generator comprised an allocated frequency of 380.8875 MHz modulated according to the ETSI standard, to simulate that of in-service hand-sets. A directional coupler and power meter were used to monitor forward and reverse power. For exposures, the RF signal was fed into the transmission line and terminated (50 W termination). For sham exposures, the RF signal was fed directly into the termination, thus bypassing the transmission line. Cell cultures were randomly assigned to exposed or sham groups.
Parameters
Measurand Value Type Method Mass Remarks
SAR 400 mW/kg average over mass measured and calculated 10 g 320-480 mW/kg
Measurement and calculation details

In order to establish a relationship between the input power of the generic TETRA signal and the SAR in the cell culture, the exposure system (including the microscope objective) was modelled using the finite integral method code, CST Microwave Studio. The electric field strength was determined along the central line of the transmission line and the calculated field strengths were then used to determine the SAR inside the perfusion medium volume. No distinction was made between the cellular component within the perfusion medium volume and the bulk perfusion medium. Dielectric properties of the cell perfusion liquid were measured at 34°C using an open ended coaxial probe and a computer controlled network analyser in the frequency region of 130 MHz-20 GHz. Using measured values for the perfusion solution, the distribution of SAR within the perfusion fluid volume was calculated. In the vicinity of the microscope objective, where the cells were recorded, the SAR varied by ±20% across the field of view, i.e. the SAR values for an average exposure of 400 mW/kg ranged from 320-480 mW/kg. Taking into account the temperature dependence, the whole volume average SAR at 30°C was determined to be 7.88% lower, and that at 37°C 3.17% higher, than that at 34°C. The input values used for the computational modelling of the transmission line were confirmed by measurement at the National Physical Laboratory. The measurements of impedance, voltage standing wave ratio and E field were in good agreement with the computed values.

Exposure 2

Main characteristics
Frequency 380.8875 MHz
Type
Exposure duration consecutive levels for a total of 40 min
Modulation
Modulation type pulsed
Duty cycle 25 %
Repetition frequency 17.6 Hz
Exposure setup
Exposure source
Setup In order to investigate the effects of exposure intensity, cell cultures were exposed for consecutive 10-min periods to baseline and TETRA RF fields at 5, 10, 20 and 50 mW/kg.
Parameters
Measurand Value Type Method Mass Remarks
SAR 5 mW/kg average over mass measured and calculated 10 g -
SAR 10 mW/kg average over mass measured and calculated 10 g -
SAR 20 mW/kg average over mass measured and calculated 10 g -
SAR 50 mW/kg average over mass measured and calculated 10 g -

Exposure 3

Main characteristics
Frequency 380.8875 MHz
Type
Exposure duration continuous for 11 min
Modulation
Modulation type pulsed
Duty cycle 25 %
Repetition frequency 17.6 Hz
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 400 mW/kg average over mass measured and calculated 10 g 320-480 mW/kg
SAR 50 mW/kg average over mass measured and calculated 10 g -

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

The data showed no evidence of any consistent or biologically relevant effect of TETRA fields on intracellular calcium in granule cells and cardiac myocytes at any of the SAR tested.

Study character:

Study funded by

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