Rats were divided into the following groups: 1) sham exposure group (for microarray analysis; n=12; investigated 3 h after exposure), 2) exposure group (for microarray analysis; n=12; investigated 3 h after exposure), 3) exposure group (for immunohistochemistry; n=6; investigated 3 h after exposure), 4) sham exposure (for RT-PCR and Western blot; n=6), 5-10) exposure groups, investigated 0 h, 0.5 h, 1 h, 3 h, 6 h, and 12 h after exposure (for RT-PCR and Western blot; n=5 or 6 (contradictory statements)).
RNA was pooled from six exposed/sham exposed hippocampi.
|Exposure duration||continuous for 20 min|
|Pulse width||2 ms|
|Packets per second||500|
|Distance between exposed object and exposure source||90 cm|
|Setup||radiation trasmitted horizontally from a rectangular horn antenna; using a reflector the radiation was redirected vertically to the exposure chamber; rats placed in Plexiglas restrainers to avoid head movement; restrainers placed inside anechoic chambers at a constant temperature of 25 - 26°C|
|Sham exposure||A sham exposure was conducted.|
Out of 2048 genes, 23 genes were upregulated and 18 were downregulated. Seven stress-associated heat shock proteins or chaperones were found among the differentially expressed genes, including HSP27 and HSP70 with a markedly increased expression.
The data from immunohistochemistry revealed that the electromagnetic field exposure caused an intensive staining for HSP27 and HSP70 in the hippocampus, especially in the pyramidal cells of cornu ammonis 3 (CA3) and granular cells of dentate gyrus. The gene expression and protein expression profiles of HSP27 and HSP70 were confirmed by RT-PCR and Western blot. Early and long-lasting expression of HSP27 and HSP70 was detected up to 12 h after exposure and exhibited differential expression patterns after exposure.
The authors conclude that the data provide evidence that exposure to electromagnetic fields elicits a stress response in the rat hippocampus. Thermal effects might have contributed to the HSP-related stress response in the rat hippocampus after radiofrequency exposure.