Study type: Medical/biological study (experimental study)

Induction of adaptive response: pre-exposure of mice to 900 MHz radiofrequency fields reduces hematopoietic damage caused by subsequent exposure to ionising radiation. med./bio.

Published in: Int J Radiat Biol 2011; 87 (7): 720-728

Aim of study (acc. to author)

To study whether an adaptive response can be induced in mice which were pre-exposed to 900 MHz radiofrequency fields and to determine the optimal power intensity needed for radiofrequency pre-exposure in order to achieve considerable "protection" from subsequent ionizing radiation-induced damage.

Background/further details

For the survival experiment, a total of 140 mice were divided into the following five groups (each group n=28): 1) 8 Gy gamma radiation alone (lethal dose), 2) radiofrequency exposure at 12 µW/cm² + gamma radiation on day 15 after the last day of exposure, 3) radiofrequency exposure at 120 µW/cm² + gamma radiation on day 15, 4) radiofrequency exposure at 1200 µW/cm² + gamma radiation on day 15, 5) positive control (free radical scavenger treatment (amifostine) + gamma radiation.
For all other experiments 144 animals were divided into the following groups (each group n=12): 1) three groups of unexposed controls, 2) 8 Gy gamma radiation (lethal dose; for organ weight evaluation) or 5 Gy gamma radiation (for all other experiments) on day 15, 3) three groups of 120 µW/cm² radiofrequency exposure (for all experiments), 4) one group at 120 µW/cm² radiofrequency exposure + 8 Gy gamma radiation (lethal dose; for organ weight evaluation) or two groups at at 120 µW/cm² radiofrequency exposure + 5 Gy gamma radiation (for colony forming units in bone marrow cells and gene expression) on day 15.
Additionally, for evaluation of colony forming units in the spleen of lethally irradiated "recipient" mice, 12 donor mice (each group n=3) were divided into 1) an unexposed control group, 2) 5 Gy gamma radiation only group, 3) group of 120 µW/cm² radiofrequency exposure and 4) group of 120 µW/cm² radiofrequency exposure + 5 Gy gamma radiation. Following gamma radiation, the mice were sacrificed, the nucletaed cells of the bone marrow were collected, pooled for each group and injected in the tail vein of recipient mice (each group n=10). Recipient mice were exposed to a lethal dose of 8.5 Gy gamma radiation 4-6 h before injection of bone marrow cells.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 900 MHz
Modulation type: CW
Exposure duration: continuous for 1 h/day for 14 days
survival experiment
Exposure 2: 900 MHz
Modulation type: CW
Exposure duration: continuous for 1 h/day for 14 days
all other experiments

General information

For the survival experiments animals were divided into five groups: i) 8.0 Gy gamma radiation on day 15 ii) 12 µW/cm² RF exposure + 8.0 Gy gamma radiation on day 15 iii) 120 µW/cm² RF exposure + 8.0 Gy gamma radiation on day 15 iv) 1200 µW/cm² RF exposure + 8.0 Gy gamma radiation on day 15 v) 500 ng/ml Amifostine + 8.0 Gy gamma radiation on day 15 For all other experiments animals were divided into four groups: i) unexposed control ii) 8.0 Gy gamma radiation (for organ weight) or 5.0 Gy gamma radiation (for all other experiments) on day 15 iii) 120 µW/cm² RF exposure iv) 120 µW/cm² RF exposure + 8.0 Gy gamma radiation (for organ weight) or 5.0 Gy gamma radiation (for all other experiments) on day 15

Exposure 1

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 1 h/day for 14 days
Additional info survival experiment
Additional info horizontally polarized
Modulation
Modulation type CW
Exposure setup
Exposure source
Chamber 5.67 m long, 2.83 m wide and 2.07 m high GTEM cell as exposure chamber
Setup signal fed through an antenna into the GTEM cell; single mouse placed in a plastic box; boxes positioned on a 1 m high table at the location inside the GTEM cell where the desired power density was measured
Parameters
Measurand Value Type Method Mass Remarks
power density 12 µW/cm² - measured - -
power density 120 µW/cm² - measured - -
power density 1,200 µW/cm² - measured - -
SAR 5.48 mW/kg - calculated whole body for 12 µW/cm²
SAR 54.8 mW/kg - calculated whole body for 120 µW/cm²
SAR 548 mW/kg - calculated whole body for 1200 µW/cm²

Exposure 2

Main characteristics
Frequency 900 MHz
Type
Exposure duration continuous for 1 h/day for 14 days
Additional info all other experiments
Additional info horizontally polarized
Modulation
Modulation type CW
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
power density 120 µW/cm² - measured - -
SAR 54.8 mW/kg - calculated whole body -

Reference articles

  • Cao Y et al. (2010): Effects of 900-MHz Microwave Radiation on gamma-Ray-Induced Damage to Mouse Hematopoietic System.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

The data indicated significant increases in survival time, in the weights of spleen and thymus, number of colony forming units in the bone marrow and spleen of lethally irradiated recipient mice, and a reduction in the hematopoietic tissue damage in radiofrequency pre-exposed mice (120 µW/cm²) which were gamma radiated (as compared with those exposed to gamma radiation alone). This was accompanied by significantly increased expression of cell cycle-related genes (different cyclins) in hematopoietic cells. The findings suggested that the 120 µW/cm² power intensity for 900 MHz radiofrequency pre-exposure was adequate and optimum to lead to the maximum protection of hematopoietic tissue damage induced by subsequent exposure to gamma radiation.
The authors conclude, that pre-exposure of mice to 900 MHz radiofrequency fields has resulted in a significant reduction in hematopoietic damage caused by subsequent exposure to ionizing radiation. This phenomenon appears to be similar to that of the "adaptive response" which is well documented in scientific literature.

Study character:

Study funded by

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