Effect of GSM microwave exposure on the genomic response of the rat brain.

Fritze K, Wiessner C, Kuster N, Sommer C, Gass P, Hermann DM, Klessing M, Hossmann KA,

Neuroscience 81: 627-639 1997

Motorola-funded

Contractors: Max Planck Institute for Neurological Research, Cologne, Germany; Institute for Neuropathology, Ruprecht Karls university, Heidelberg, Germany; and Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.

This study explored possible acute effects of pulsed or continuous wave GSM signals on the central nervous system of exposed rats, as determined by measured levels of the genes hsp70 and c-fos. Exposed rats were subject for four hours to SARs of 0.3mW/g, 1.5mW/g brain tissue and 7.5mW/g brain tissue.

The researchers concluded there were no exposure-related genomic changes in SARs up to 1.5mW/kg which compares to exposure limits of 1.6W/kg or 2 W/kg established by internationally recognised RF safety standards for wireless telephones and other portable radio products.

At the higher level of exposure (7.5W/kg), the researchers found minor focal expression of hsp70, but concluded it was most likely the combined effect of immobilisation and thermal effects related to the high SAR. The researchers also found no effects on protein expression or cell proliferation.

Another abstract of the same study

The acute effect of global system for mobile communication (GSM) microwave exposure on the genomic response of the central nervous system was studied in rats by measuring changes in the messenger RNAs of hsp70, the transcription factor genes c-fos and c-jun and the glial structural gene GFAP using in situ hybridization histochemistry. Protein products of transcription factors, stress proteins and marker proteins of astroglial and microglial activation were assessed by immunocytochemistry.

Cell proliferation was evaluated by bromodeoxyuridine incorporation. A special GSM radiofrequency test set, connected to a commercial cellular phone operating in the discontinuous transmission mode, was used to simulate GSM exposure. The study was conducted at time averaged and brain averaged specific absorption rates of 0.3 W/kg (GSM exposure), 1.5 W/kg (GSM exposure) and 7.5 W/kg (continuous wave exposure), respectively. Immediately after exposure, in situ hybridization revealed slight induction of hsp70 messenger RNA in the cerebellum and hippocampus after 7.5 W/kg exposure, but not at lower intensities.

A slightly increased expression of c-fos messenger RNA was observed in the cerebellum, neocortex and piriform cortex of all groups subjected to immobilization, but no differences were found amongst different exposure conditions. C-jun and GFAP messenger RNAs did not increase in any of the experimental groups. 24 h after exposure, immunocytochemical analysis of FOS and JUN proteins (c-FOS, FOS B, c-JUN JUN B, JUN D), of HSP70 or of KROX-20 and -24 did not reveal any alterations. Seven days after exposure, neither increased cell proliferation nor altered expression of astroglial and microglial marker proteins were observed.

In conclusion, acute high intensity microwave exposure of immobilized rats may induce some minor stress response but does not result in lasting adaptive or reactive changes of the brain.