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Medizinische/biologische Studie (experimentelle Studie)

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

[Membranpotenzial und Ströme isolierter Herzmuskel-Zellen, die bei gepulsten hochfrequenten Feldern exponiert wurden].

Veröffentlicht in: Bioelectromagnetics 1999; 20 (8): 497-511

Ziel der Studie (lt. Autor)

Es sollte geprüft werden, ob Felder, die von GSM-Telefonen (900 und 1800 MHz) und anderen Kommunikationsgeräten, wie Polizeifunkanlagen (180 MHz) ausgesendet werden, in der Lage sind, elektrische Charakteristika erregbarer Zellen zu beeinflussen (ob der L-Typ Ca2+-Fluss in Gegenwart solcher Felder beeinflusst wird).

Endpunkt

Exposition/Befeldung (teilweise nur auf Englisch)

Exposition Parameter
Exposition 1: 1.800 MHz
Modulationsart: gepulst
Expositionsdauer: kontinuierlich für 2 min
Exposition 2: 900 MHz
Modulationsart: gepulst
Expositionsdauer: kontinuierlich für 2 min
Exposition 3: 900 MHz
Modulationsart: gepulst
Expositionsdauer: kontinuierlich für 2 min
Exposition 4: 180 MHz
Modulationsart: CW
Expositionsdauer: kontinuierlich für 2 min
Allgemeine Informationen
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.
Exposition 1
Hauptcharakteristika
Frequenz 1.800 MHz
Typ
Charakteristik
  • gerichtetes Feld
Expositionsdauer kontinuierlich für 2 min
Modulation
Modulationsart gepulst
Anstiegszeit 2,5 µs
Abfallzeit 2,5 µs
Tastgrad 12,5 %
Folgefrequenz 217 Hz
Pulsart rechteckig
Zusatzinfo GSM-standard
Expositionsaufbau
Expositionsquelle
Kammer 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.
Aufbau 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.
Zusatzinfo 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.
Parameter
Messgröße Wert Typ Methode Masse Bemerkungen
Leistung 1,8 W Spitzenwert - - 0,2; 1,2 und 1,8 W für Meerschweinchen-Zellen
SAR 720 mW/kg Mittelwert über Zeit berechnet nicht spezifiziert 80, 480 und 720 mW/kg für Meerschweinchen-Zellen
Leistung 2,2 W Spitzenwert - - 1,5; 1,8 und 2,2 W für Ratten-Zellen
SAR 880 mW/kg Mittelwert über Zeit berechnet nicht spezifiziert 600, 720 und 880 mW/kg für Ratten-Zellen
Mess- und Berechnungsdetails
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.
Exposition 2
Hauptcharakteristika
Frequenz 900 MHz
Typ
Charakteristik
  • gerichtetes Feld
Expositionsdauer kontinuierlich für 2 min
Modulation
Modulationsart gepulst
Anstiegszeit 2,5 µs
Abfallzeit 2,5 µs
Tastgrad 12,5 %
Folgefrequenz 217 Hz
Pulsart rechteckig
Zusatzinfo GSM-standard. The spectral width of the carrier signal was 3.6 kHz.
Expositionsaufbau
Expositionsquelle
Parameter
Messgröße Wert Typ Methode Masse Bemerkungen
SAR 250 mW/kg Mittelwert über Zeit berechnet nicht spezifiziert -
Mess- und Berechnungsdetails
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.
Exposition 3
Hauptcharakteristika
Frequenz 900 MHz
Typ
Charakteristik
  • gerichtetes Feld
Expositionsdauer kontinuierlich für 2 min
Modulation
Modulationsart gepulst
Anstiegszeit 2,5 µs
Abfallzeit 2,5 µs
Tastgrad 12,5 %
Folgefrequenz 217 Hz
Pulsart rechteckig
Zusatzinfo GSM-standard. The spectral width of the carrier signal was 3.6 kHz.
Expositionsaufbau
Expositionsquelle
Kammer Design of the TEM-cell and experimental setup have been described in detail in the reference article.
Parameter
Messgröße Wert Typ Methode Masse Bemerkungen
SAR 15 mW/kg Mittelwert über Zeit berechnet nicht spezifiziert -
Exposition 4
Hauptcharakteristika
Frequenz 180 MHz
Typ
Charakteristik
  • gerichtetes Feld
Expositionsdauer kontinuierlich für 2 min
Modulation
Modulationsart CW
Zusatzinfo CW was used to simulate the German police communication standard working with FM.
Expositionsaufbau
Expositionsquelle
Parameter
Messgröße Wert Typ Methode Masse Bemerkungen
SAR 80 mW/kg Mittelwert über Zeit berechnet nicht spezifiziert -
Referenzartikel
  • Wolke S et al. (1996): Calcium homeostasis of isolated heart muscle cells exposed to pulsed high-frequency electromagnetic fields.
Exponiertes System:

Methoden Endpunkt/Messparameter/Methodik

Untersuchtes Material:
Untersuchungszeitpunkt:
  • während der Befeldung
  • nach der Befeldung

Hauptergebnis der Studie (lt. Autor)

Die Ergebnisse zeigen, dass die untersuchten hochfrequenten Felder auf eine Reihe elektrischer Membranparameter, wie Ruhemembranpotential und Aktionspotential, nicht störend wirken.
Studienmerkmale:

Studie gefördert durch

  • Forschungsgemeinschaft Funk e.V. (FGF) (Research Association for Radio Applications), Germany

Themenverwandte Artikel

  • Daus AW et al. (2011): Electromagnetic exposure of scaffold-free three-dimensional cell culture systems.
  • Platano D et al. (2007): Acute exposure to low-level CW and GSM-modulated 900 MHz radiofrequency does not affect Ba(2+) currents through voltage-gated calcium channels in rat cortical neurons.