Adaptive response: Former studies have shown that different cell types exposed to an extremely small adaptation dose of a genotoxic agent are less susceptible to the induction of a genetic damage when given a higher challenge dose of the same or a similar genotoxic agent.
Blood lymphocytes of four male healthy donors were stimulated for 24 h with phytohaemagglutinin and then exposed for 20 hours to an adaptive dose of 1950 MHz radiofrequency field to a specific absorption rate of 0.3 W/kg or sham exposed. This was followed by a challenge dose of x-radiation (1.0 or 1.5 Gy). Cells were collected after 72 h total culture period and the frequency of micronuclei was recorded.
Further experiments were performed with X-radiation and mitomycin C as an adaptive dose. The results are not presented here.
|Exposure duration||continuous for 20 hours|
|Chamber||two exposure chambers of rectangular waveguides (WR 430) housed (together with sham waveguide) in commercial incubator; waveguides fed by amplified signal of a signal generator|
|Setup||samples placed on four-layer plexiglass stand with 35 mm Petri dishes on each layer; the Petri dishes containing the diluted blood from each donor were kept in the outer positions and exposed to 0.3 W/kg, while dummy samples were placed in the inner positions of the incubator (37.0 ± 0.5°C, 95% air, 5% carbon dioxide)|
|Sham exposure||A sham exposure was conducted.|
Cell cultures exposed to a radiofrequency field as an adaptive dose before treated with a challenge dose of 1.5 Gy x-radiation (but not 1.0 Gy) showed a significant decrease in the number of micronuclei compared to those treated with x-radiation alone. However, a large variability was observed between the donors. The proliferation index was similar between cell cultures pre-exposed to an adaptive dose of radiofrequency fields and subsequently treated with X-radiation and those cell cultures treated with X-radiation alone.
The authors conclude that exposure of human lymphocytes to radiofrequency fields exhibits an adaptive response by resisting genotoxic effects from subsequent exposure to X-radiation.