For each donor (n=6) several experimental conditions were considered to check for a possible different sensitivity through the cell cycle (via micronucleus assay): (1) intermittent exposures of un-stimulated lymphocytes (resting cells) for 24 h, followed by 44 h exposure after phytohemagglutinin stimulation, to test radiofrequency exposure in G0 phase-G1 phase-S phase-G2 phase stages; (2) intermittent exposures for 44 h after phytohemagglutinin stimulation, to test radiofrequency exposure in G1 phase-S phase-G2 phase stages; (3) intermittent exposures of un-stimulated lymphocytes (resting cells) for 24 h before phytohemagglutinin stimulation. For comet assay un-stimulated lymphocytes (resting cells) were exposed for 24 h.
Positive controls were performed by treating cells with mitomycin C and methyl methanesulfonate for micronucleus and comet assays, respectively.
|Chamber||The TEM cell was placed vertically inside an incubator equipped with air circulation systems.|
|Setup||Two 25-ml Pyrex flasks filled with 10 ml of whole blood culture were placed 1 cm from each other on each side of the septum over a 1.5-mm thick Plexiglas shelf and radiated from the bottom.|
|Sham exposure||A sham exposure was conducted.|
|Additional info||Several independent temperature measurements were carried out in dummy cultures (flasks filled with culture medium) applying constant input power of 6 W for 6 min. A temperature increase of 0.67 ± 0.35 °C was measured, but the "off" period (2 h) was long enough to restore the initial conditions.|
The data showed that intermittent exposures in different stages of the cell cycle to the UMTS signal at SAR value of the current European safety limit do not induce genotoxic or cytotoxic effects in human lymphocytes.