Ammari M, Gamez C, Lecomte A, Sakly M, Abdelmelek H, De Seze R.(2010). GFAP expression in the rat brain following sub-chronic exposure to a 900 MHz electromagnetic field signal. Int J Radiat Biol. 86(5):367-75.
Astrocytes, the principal glial cell type, are involved in many cellular processes in the brain. Activated astrocytes are involved in reactive gliosis, the process that occurs as a result of tissue brain damage. Glial fibrillary acidic protein (GFAP) is highly specific to cells in the astroglial lineage. Its level increases at the site of damage and can appear from 24 hours to many days after injury.
The objective of this study was to determine whether sub-chronic exposure of the head alone to the radiofrequency (RF) signal induces persistent astroglial activation in the brain.
Male Sprague-Dawley rats were exposed to 900 MHz signal for 45 minutes per day at a brain-averaged specific absorption rate (SAR)=1.5 W/Kg or for 15 minutes per day at a brain-averaged SAR=6 W/Kg for 8 weeks. A total of 48 rats were used in these experiments. Twenty four rats were sacrificed 3 days after exposure termination and 24 rats were sacrificed 10 days after exposure termination. Within these groups of 24 rats:
- 6 rats were exposed for 15 minutes at SAR=6 W/Kg,
- 6 rats were exposed for 45 minutes at SAR=1.5 W/Kg,
- 6 rats were sham-exposed
- 6 rats were given no treatment or manipulation (cage control).
GFAP expression was measured in five areas of the brain by immunohistochemistry.
Three days post-treatment, GFAP levels in rats exposed to SAR=1.5 for 45 minutes and to SAR=6 W/kg for 15 minutes were higher than in sham-exposed rats in all the brain regions examined (prefrontal cortex, cerebellar cortex, dentate gyrus of the hippocampus, lateral globus pallidus of the striatum and the caudate putamen). Ten days after exposure, the increase in GFAP level was significant in prefrontal cortex, dentate gyrus and lateral globus pallidus of rats exposed to SAR=6 W/Kg for 15 minutes, and in the lateral globus pallidus of rats exposed to SAR=1.5 W/Kg for 45 minutes.
Interpretation and Conclusion
The results of this study show that sub-chronic exposure to RF signal for 45 minutes per day at SAR=1.5 W/Kg or for 15 minutes per day at SAR=6 W/Kg results in an increase in GFAP expression in the rat brain 3 days after exposure. In several brain regions, this effect persists for 10 days suggesting the occurrence of neuronal damage.