Auteurs
Authors
Hoyto A, Sokura M, Juutilainen J, Naarala J. (2008). Radiofrequency radiation does not significantly affect ornithine decarboxylase activity, proliferation, or caspase-3 activity of fibroblasts in different physiological conditions. International Journal of Radiation Biology 84( 9):727 – 733.

Background
Biological effects of mobile phone RF radiation have been studied in several in vitro studies on cellular processes, such as cellular ornithine decarboxylase (ODC) activity, proliferation, and apoptosis (programmed cell death). These cellular processes are important because of their potential influence in the development of human cancers.

Objective
The objective of this research was to evaluate whether variations in the physiological state of cells could be the reason for inconsistent results from in vitro studies on biological effects of RF.

Methods
Cells stressed with (1) serum deprivation, (2) stimulated with fresh medium or (3) untreated were exposed to 872 MHz continuous wave or pulse RF at a specific absorption rate (SAR) of 5 W/kg. Control cells were not exposed to any RF but were sham-exposed. Three endpoints were chosen to study the effects of RF exposure on uncontrolled cellular growth:

(1) The activity of Ornithine decarboxylase (ODC) enzyme that regulates cell proliferation.    Activity of the ODC was measured after 1 or 24 hours of RF exposure.
(2) The activity of Caspase-3 enzyme which measures programmed cell death, a mechanism to protect against cancer, was measured after 1 hour of RF exposure.   
(3) Cell proliferation was measured after 24 hours of RF exposure.

Statistical analysis was conducted to see whether the differences in the values for the three endpoints were significant or just due to chance.

Results
The results showed that there was no statistically significant difference in the ODC activity, cellular proliferation, or Caspase-3 activity between treated and non-treated cells. There was also no statistically significant difference in the three endpoints between cells exposed to RF radiation and stressed (by serum deprivation), or stimulated (by fresh medium) and cells which were stressed or stimulated only (no RF exposure). However, cells exposed to both RF radiation and serum deprivation showed consistently (but not statistically significant) higher caspase-3 activity than cells exposed to serum deprivation only.

Interpretation
The results are in agreement with the majority of previous studies which showed no effect of RF on cellular proliferation and other studies which showed no effects on Caspase-3 activity.  Some of the previous studies have shown decreased ODC activity in cells exposed to RF radiation at SAR > 6 W/kg, but this effect was shown to be due to temperature increase rather than to RF radiation exposure.

Conclusion
The authors concluded that their results provide evidence that exposure of cells to 872 MHz pulse-modulated or continuous wave RF radiation at 5 W/kg has no effects on ODC activity, proliferation, or caspase-3 activity. There was also no evidence that altered physiological state (stimulation or stress) modulate cellular response to RF radiation.

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