Study type: Medical/biological study (experimental study)

Exposure to 2.45 GHz electromagnetic fields induces hsp70 at a high SAR of more than 20 W/kg but not at 5W/kg in human glioma MO54 cells med./bio.

By: Tian F, Nakahara T, Wake K, Taki M, Miyakoshi J
Published in: Int J Radiat Biol 2002; 78 (5): 433-440
Download citation in RIS format

Aim of study (acc. to author)

To determine potential hazard from exposure to a 2.45 GHz field on the expression of heat-shock protein 70 (hsp70) in MO54 cells.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.45 GHz
Modulation type: CW
Exposure duration: continuous for 2, 4, 8, 16, and 24 h
  • SAR: 100 W/kg mean (5, 20, 50, and 100 W/kg in the middle ring)
  • SAR: 78 W/kg mean (3.9, 16, 39, and 78 W/kg in the outer ring)
  • SAR: 25 W/kg mean (1.3, 5, 13, and 25 W/kg in the inner ring)

Exposure 1

Main characteristics
Frequency 2.45 GHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 2, 4, 8, 16, and 24 h
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber Four loop antennas on the bottom of the cavity excited travelling waves in TE01 mode, and a metal lid on the top generated standing waves. The incubator-like atmosphere inside the cavity with 95% air and 5% CO2 and >95% humidity was maintained at 37°C. Two cavities for MW and sham exposure were placed in a thermostatic chamber at 38°C (or 40°C?) to prevent condensation on their inner walls.
Setup The cell suspensions were contained in a 140-mm annular culture plate that was irradiated from the bottom. The plate had three radial compartments (inner, middle, and outer ring) allowing different exposure levels for cell suspensions of 3.3, 12.3, and 24.7 ml volume. Thermostated water circulated in a tank beneath the plate.
Sham exposure A sham exposure was conducted.
Additional info A raised temperature control group was incubated at 39°C in a conventional incubator.
Parameters
Measurand Value Type Method Mass Remarks
SAR 100 W/kg mean estimated - 5, 20, 50, and 100 W/kg in the middle ring
SAR 78 W/kg mean estimated - 3.9, 16, 39, and 78 W/kg in the outer ring
SAR 25 W/kg mean estimated - 1.3, 5, 13, and 25 W/kg in the inner ring
Measurement and calculation details

A power meter was used to monitor input and reflected powers. The SAR in the plate was estimated by thermography [Guy, 1987] at 50 W for 15 s using an infrared camera.

Reference articles

  • Guy AW (1987): Dosimetry associated with exposure to non-ionizing radiation: very low frequency to microwaves

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

Radiofrequency electromagnetic field can produce an increased level of hsp70 expression at SAR levels above 20 W/kg, even when the effect of raised temperature is taken into account. Cell survival decreased to about 30% after exposure to radiofrequency electromagnetic field for 24h at an average SAR of 100 W/kg. A slight increase in hsp70 was found in cells in both the inner and outer rings of the plate after exposure at SAR levels of 25 and 78 W/kg for 2h. Except for an SAR of 5 W/kg hsp70 expression increased with increasing exposure time. The expression level of hsp70 for the exposed cells was greater than that for the raised temperature control.

Study character:

Study funded by

Related articles