Study type: Medical/biological study (experimental study)

Measurements of alkali-labile DNA damage and protein-DNA crosslinks after 2450 MHz microwave and low-dose gamma irradiation in vitro med./bio.

By: Lagroye I, Hook GJ, Wettring BA, Baty JD, Moros EG, Straube WL, Roti Roti JL
Published in: Radiat Res 2004; 161 (2): 201-214
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Aim of study (acc. to author)

To determine whether 2450 MHz microwave irradiation induces alkali-labile DNA damage and/or DNA-protein or DNA-DNA crosslinks in C3H10T(1/2) cells.

Background/further details

To evaluate the potential of these microwaves to induce DNA-DNA or DNA-protein crosslinks, microwave-exposed cells were treated with 4 Gy of gamma radiation and the DNA migration pattern in the comet assay was evaluated. The presence of DNA-DNA or DNA-protein crosslinks in cells containing DNA damage has been shown to reduce the level of DNA migration found in the comet assay.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2,450 MHz
Modulation type: CW
Exposure duration: continuous for 2 h

General information

Each experiment included the following treatment groups: sham exposed, MW exposed, sham/γ-ray exposed, and MW/γ-ray exposed.

Exposure 1

Main characteristics
Frequency 2,450 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 2 h
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber Chamber with up to 10 radial transmission lines (RTLs), consisting of parallel-plates with aluminium bottom plate and a metal-faced composite top plate [Moros et al., 1999].
Setup The electric field of the waves propagating radially outward was perpendicular to the cell layer. The tangential magnetic field was perpendicular to the EF and the propagation direction.
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 1.9 W/kg mean measured and calculated - ± 1.0 W/kg
Additional parameter details

Cells exposed to ionising radiation, either after MW or CDDP treatment or alone as a positive control, were protected from light and irradiated in suspension on ice with 4 Gy of 137Cs γ-rays at a dose rate of 7.34 Gy/min.

Measurement and calculation details

The average SAR at the bottom of the flasks was determined using a fast temperature differential measurement technique [Pickard et al., 1999] and agreed well with FDTD modelling results [Pickard et al., 2000]. The measured SAR value does not include the uncertainty of ±10% due to standard power measurements.

Reference articles

  • Pickard WF et al. (2000): Experimental and numerical determination of SAR distributions within culture flasks in a dielectric loaded radial transmission line
  • Moros EG et al. (1999): The radial transmission line as a broad-band shielded exposure system for microwave irradiation of large numbers of culture flasks
  • Pickard WF et al. (1999): Simplified model and measurement of specific absorption rate distribution in a culture flask within a transverse electromagnetic mode exposure system
  • Chou CK et al. (1996): Radio frequency electromagnetic exposure: tutorial review on experimental dosimetry

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

Ionizing gamma radiation (4 Gy) induced significant DNA damage. However, no DNA damage could be revealed after exposure to 2450 MHz CW (continuous wave) microwaves alone. The crosslinking agent CDDP (cis-diamine dichloroplatinum II (cisplatin), used as a positive control) significantly reduced both the comet length and the normalized comet moment in the cells irradiated with 4 Gy gamma rays. In contrast, 2450 MHz microwaves did not impede the DNA migration induced by gamma radiation. When control cells were treated with proteinase K, both parameters increased in the absence of any DNA damage. However, no additional effect of proteinase K was seen in samples exposed to the microwaves or in samples treated with the combination of microwaves and radiation. On the other hand, proteinase K treatment was ineffective in restoring any migration of the DNA in cells pretreated with CDDP and exposed to gamma rays. When DNA-protein crosslinks were specifically measured, the authors found no evidence for the induction of DNA-protein crosslinks or changes in amount of the protein.
Thus, the results show that a 2-h exposure to 1.9 W/ kg of 2450 MHz CW microwaves did not induce measurable alkali-labile DNA damage or DNA-DNA or DNA-protein crosslinks.

Study character:

Study funded by

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