To study HSP70 gene expression and protein expression in human trophoblast cells after exposure to 1.8 GHz (continuous wave and different GSM signals) to assess the possible effects of time and modulation schemes on cell responses.
Experiments for each modulation scheme were carried out with three different exposure periods (4, 16 and 24 hours). For each condition, six independent experiments were performed for gene expression and protein expression. Positive controls were performed with 43 °C heat (1 h) and negative controls were performed in the incubator.
Modulation type: CW
Modulation type: pulsed
Modulation type: pulsed
|Chamber||The exposure system was developed and built following the specifications in [Schonborn et al., 2000]. Two 128.5 x 65 x 424 mm³ brass single-mode waveguide resonators equipped with ventilators and air temperature probes were placed inside one of the two incubators.|
|Setup||Six 35-mm Petri dishes per resonator, each containing 3 ml of medium, were arranged in two stacks using a plastic holder and were placed in the H-field maximum of the standing wave (E-polarization).|
|Sham exposure||A sham exposure was conducted.|
|Additional info||Within each experiment, six dishes each were RF and sham exposed. Signal characteristics and the exposure/sham condition were assigned to the two waveguides by a computer-controlled signal unit ensuring blinded conditions.|
|SAR||2 W/kg||average over time||measured and calculated||-||-|
|Duty cycle||12.5 %|
|Repetition frequency||217 Hz|
GSM-Talk signal (33% speaking and 67% hearing) with temporal changes between GSM-217 Hz and GSM-DTX (transmission reduced to 12 active frames per 104 frames) resulting in 2, 8, and 217 Hz modulation components
There were no significant differences in cell viability between all groups. No significant differences in either HSC70 or HSP70 protein expression were observed between radiofrequency electromagnetic field exposed and sham exposed samples. After exposure to heat shock the trophoblast cells showed a significant overexpression of the HSP70 protein, while HSC70 was unaffected. The HSP70-A, HSP70-B and HSC70 transcripts did not change in cells exposed to radiofrequency electromagnetic fields. Levels of the HSP70-C transcript were significantly enhanced after 24 hours exposure to GSM-217 Hz and reduced after 4 hours and 16 hours exposure to GSM-talk signals.
The results suggest that the expression analysis for multiple transcripts, though encoding the same or similar protein products, can identify subtle changes that would not be detected at the protein level.