The effects of exposure of rats to a 900 MHz electromagnetic field on the spatial memory, neuronal and blood brain barrier damage and the potential underlying mechanisms of action should be investigated.
108 rats were divided into 3 groups (n=36 each): 1) sham exposure, 2) exposure to the magnetic field for 14 days and 3) 28 days. In each group, 3 rats were used for electron microscopy, 6 were used for immunohistochemistry, 12 for the evans blue assay, 6 for Western blot and 9 for the Morris water maze.
Heme oxygenase-1 (HO-1) is a marker for oxidative stress. MAPK phosphatase-1 (mkp-1) regulates the activity and expression of ERK 1 and 2. The authors hypothesized that the mkp-1/ERK pathway is potentially involved in the regulation of HO-1, the damaging of the blood brain barrier and resulting cognitive impairments.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
900 MHz
Exposure duration:
continuous for 3 h/day for 14 days
|
|
|
Exposure 2:
900 MHz
Exposure duration:
continuous for 3 h/day for 28 days
|
| Frequency | 900 MHz |
|---|---|
| Type | |
| Exposure duration | continuous for 3 h/day for 14 days |
| Exposure source |
|
|---|---|
| Distance between exposed object and exposure source | 1 m |
| Setup | four rats were exposed simultaneously in an immobilization apparatus with their heads towards the antenna at a distance of at least 1 m; the propagation direction of the signal was in the direction of the long-axis of the rats; the position of the rats during exposure on each day was altered |
| Sham exposure | A sham exposure was conducted. |
| Frequency | 900 MHz |
|---|---|
| Type | |
| Exposure duration | continuous for 3 h/day for 28 days |
| Exposure source |
|
|---|
The spatial memory was significantly impaired after 28 days of exposure (group 3) compared to the 14-day exposure group (group 2) and sham exposure.
The neuronal ultrastructure was changed in groups 2 and 3 compared to sham exposure with edema between neurons and blood vessels. Group 3 showed additional swollen or missing organelles and cytoplasmic vacuolization in neurons.
The level of HO-1 was significantly higher in both exposure groups compared to the sham exposure and in group 3 compared to group 2.
In immunohistochemical analysis, a significant higher level of albumin was found in group 3 in the hippocampus and cortex compared to group 2 and sham exposure, but albumin could also be detected in neurons of group 2. Additionally, a significant higher amount of evans blue could be detected in groups 2 and 3 compared to sham exposure. The mkp-1 expression was significantly up-regulated and ERK phosphorylation significantly reduced in group 3 compared to the sham exposure.
The authors conclude, that exposure of rats to a 900 MHz electromagnetic field could impair the spatial memory and damage the blood brain barrier and that the mkp-1/ERK signaling pathway may be involved in this process.
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