Autores

Cao Y, Xu Q, Jin Z-D, Zhou Z, Nie J-H, Tong J. Induction of adaptive response:  Pre-exposure of mice to 900 MHz radiofrequency fields reduces hematopoietic damage cause by subsequent exposure to ionising radiation. Int. J. Radiat. Biol. Early Online, 2011.

Background
Everyday exposure to radiofrequency fields (RF) has shown to be protective against subsequent exposure to ionising radiation by some investigators.  For example, animals that were first exposed to RF fields and then ionising radiation had a greater survival rate than animals that were exposed to ionising radiation alone.  Researchers believe that pre-exposure to RF initiates an ‘adaptive response’ that protects the body against the subsequent harm of ionising radiation exposure.

Objective
The objective of this study was to investigate the protective effect of pre-exposure to RF fields for mice exposed to lethal doses of ionising radiation.
   
Methods
Five different sets of experimental groups of mice were used in the study: 
1) The first experimental set was used to determine optimal adaptive response initiation in mice before ionising radiation exposure.  Mice were exposed to three different power intensities (12, 120, and 1200 μW/cm2) of 900 MHz RF for 1 hour/day for 14 days before exposure to 8 Gy of gamma-radiation.  The optimum intensity was determined to be 120 μW/cm2.
2) The second experimental set investigated blood forming organ weights (thymus and spleen) after exposure to 8 Gy of gamma-radiation with and without 1 hour/day, 14 day pre-exposure to the optimum RF field intensity.  Organ health was determined 5 days after radiation exposure.
3)  The third experimental set investigated bone marrow health and how blood cell production was affected after exposure to 5 Gy of gamma-radiation with and without 1 hour/day, 14 day pre-exposure to the optimum RF field intensity.  Blood production was determined 3, 6, 9 and 12 days after gamma-radiation exposure.
4) The fourth experimental set investigated the ability of the bone marrow cells to transfer the ‘adaptive response’ to another mouse.  Mice were subjected to the same procedures as in group 3; bone marrow cells were isolated from these ‘donor’ mice 4-6 hr after irradiation, and these cells were then injected into a ‘recipient’ mouse that had been exposed to 8.5 Gy gamma-radiations (4-6 hours before).   Nine days later the spleen was excised and tested for blood-forming capacity. 
5)  The fifth experimental set determined whether there was an increased expression of adaptive proteins in the spleen.  This experiment was carried out the same as #3 but the spleens were isolated at 3, 6, 9 and 12 days. 

Results
Significant differences were found between groups that were pre-exposed to RF fields before ionising radiation exposure compared to groups that were exposed to ionising radiation alone:

  1.  Group 1:  There was a significant increase in survival rate of mice pre-exposed to RF fields at the intensity of 120 μW/cm2.
  2. Group 2:  The organ weights of thymus and spleen were significantly reduced compared to unexposed organs; however, organs that were pre-exposed to RF fields showed a significant increase in weight.
  3. Group 3:  There was a significant increase in level of protection from RF fields for blood production from day 6 to 12.
  4. Group 4:  Cells from ‘donor’ mice that had been exposed to RF fields only had a protective effect; however ‘donor’ cells from mice that had been pre-exposed to RF fields and then exposed to ionising radiation were not protective.
  5. Mice pre-exposed to RF fields and then ionising radiation showed increased expression of many protective proteins.

 
Interpretation and Limitations
The authors suggest that RF field radiation induces a set of genes that have a protective effect against the harm done by ionising radiation exposure.

Conclusions

This study suggests that pre-exposure to non-ionising 900 MHz RF induces an ‘adaptive response’ that reduces damage to blood forming processes caused by ionising radiation.


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