The firefly luciferase gene was transfected into human embryonic kidney cells as the enzyme activity of luciferase is a sensitive marker for cellular stress.
Cells were either sham exposed or exposed for up to 90 minutes. All results represent means of 3 repeated experiments with 3 measurements, respectively.
|Exposure duration||continuous for up to 90 minutes|
|Chamber||cell monolayer inside a 35 mm petri dish|
|Setup||waveguide unit consisted of an aluminum box (60 x 17 x 17 cm) with one probe at each end generating the field; 4 discs (stubs) were used for impedance matching; reactangular waveguide was placed in an incubator and equipped with two fans working in opposite directions at both ends for temperature control (37 ± 0.3°C in incubator; temperature change in dishes was 0.07±0.03 °C (range 0.02-0.1°C) during exposure); field inhomogeneity was below 30%|
|Sham exposure||A sham exposure was conducted.|
The luciferase enzyme activity was significantly decreased after 30 and 45 minutes and significantly increased after 60 minutes of exposure compared to sham exposure.
The reactive oxygen species content was significantly increased after 15, 30 and 45 minutes of exposure compared to sham exposure. The enzyme activity of superoxide dismutase was significantly increased after 30 and 45 minutes of exposure compared to sham exposure. The enzyme activity of catalase was significantly increased after 15, 30, 45 and 60 minutes of exposure compared to sham exposure. The content of reduced glutathione was significantly increased after 45 minutes of exposure, whereas the content of malondialdehyde was significantly reduced after 45 minutes compared to sham exposure.
The enzyme activity of caspase 3 and 7 was significantly increased after 45 and 90 minutes, but not after 60 minutes of exposure compared to sham exposure, showing no distinct indication for apoptosis.
The authors conclude, that an acute exposure of transgenic human embryonic kidney cells to a 940 MHz electromagnetic field could cause oxidative stress which is followed by an anti-oxidative response, what is represented by the luciferase enzyme activity.