Auteurs

Nittby H, Brun A, Eberhardt J, Malmgren L, Persson BR, Salford LG. Increased blood-brain barrier permeability in mammalian brain 7 days after exposure to the radiation from a GSM-900 mobile phone. Pathophysiology. 2009 Apr 1 Ahead of print.

Introduction
Blood brain barrier (BBB) is essential for protecting the mammalian brain from potentially harmful substances circulating in the blood. The passage of substances through BBB is highly restricted. The membrane controls the exchange of nutrients and other essential substances from the general circulation to the central nervous system (CNS). If the BBB is damaged, toxic materials can leak into the brain.  Previous studies have shown that radiation exposure can increase BBB permeability after 2 hours of mobile phone exposure and also after 14 and 50 days of exposure. However, in other studies, electromagnetic frequency failed to induce alterations in permeability of the BBB.

Objective
The purpose of the current study is to investigate the effects of electromagnetic frequency on rat brain 7 days after exposure from GSM exposure at 915MHz for 2 hours at non-thermal energy levels of 0.12 mW/kg, 1.2 mW/kg, 12 mW/kg and 120 mW/kg and to compare the effects with previous studies reporting effects immediately and 14 days after exposure.

Methods
Animals were exposed to electromagnetic frequency in the same traverse electromagnetic transmission line cell (TEM-cells). A GSM mobile phones operating at 900 MHz frequency band, with programmable power output was connected to TEM-cells. A total of 48 inbred male and female Fischer rats were exposed to different levels of non-ionizing radiation (see above) for 2 hours.  The animals were kept for 7 days after exposure and then sacrificed. The brain material was fixed in situ through saline perfusion and studied for albumin extravasation (presence of albumin in the brain indicating leakage of the BBB). Regarding neuronal damage, brain tissue was examined histopathologically by a neuropathologist and was judged as occasional, moderate, or abundant damage.

Results
After 7 days of recovery time, albumin foci found significantly more often among exposed rats (25%) than among non-exposed sham control rats (P=0.04). There was also a small but significant correlation between the exposure level and the occurrence of albumin foci (Spearman analysis r=0.33; p=0.04). Pairwise exposure between different exposure levels and sham exposed animals revealed statistically significant differences of exposure level of 0.12 mW/kg and 120mW/kg.

Discussion and Conclusions
The current study provided evidence that GSM exposure results in disruption of the permeability of the blood brain barrier (BBB) even 7 days after exposure. This exposure level was below the thermal exposure level in humans.  The results were in agreement with previous studies showing effects on BBB permeability immediately and after 7 days of exposure. One remarkable observation in this study in that exposure at very low whole-body average power densities gives rise to a pronounced albumin leakage (at levels of 0.12mW/kg). This increased BBB permeability at very low energy exposure levels may indicate that the effect of electromagnetic frequency exhibit a U-shaped response. The impairment of BBB permeability 7 days after exposure indicates the persistence of the changes in the brain permeability.


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