To evaluate the extent of a primary DNA damage in peripheral blood leukocyte in mice pre-exposed to 900 MHz radiofrequency (120 mW/cm²) for 4 hours/day for different days (as adaptive dose) and then subjected to 3 Gy gamma radiation (as challenge dose).
Adaptive response: It is known that different cell types that were exposed to an extremely small adaptation dose of a genotoxic agent are less susceptible to the induction of genetic damage when given a higher challenge dose of the same or similar genotoxic agent. The induction of an adaptive response was shown to be influenced by several factors (e.g. the dose used for adaptation, the dose rate, the time between the adaptation and challenge doses).
Mice were divided into several groups of 5 mice each: (1) unexposed controls, (2) acute exposure to gamma radiation (3 Gy, 60Co), (3) 900 MHz radiofrequency exposure for 4 hours/day for 1, 3, 5, 7 and 14 days, and (5) the same radiofrequency exposure periods + 3 Gy gamma radiation given at 4 hour after radiofrequency exposure on days 1, 3, 5, 7 and 14.
Exposure | Parameters |
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Exposure 1:
900 MHz
Exposure duration:
continuous for 4 hours/day for 1, 3, 5, 7 and 14 days
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Mice were divided into several groups of 5 mice each: (1) unexposed controls (2) acute exposure to gamma radiation (3 Gy, 60Co) (3) 900 MHz radiofrequency exposure for 4 hours/day for 1, 3, 5, 7 and 14 days (five groups) (4) the same radiofrequency exposure periods + 3 Gy gamma radiation given at 4 hour after radiofrequency exposure on days 1, 3, 5, 7 and 14 (five groups)
Frequency | 900 MHz |
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Type | |
Exposure duration | continuous for 4 hours/day for 1, 3, 5, 7 and 14 days |
Exposure source | |
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Setup | mice were restrained and exposed individually in small plastic boxes |
Measurand | Value | Type | Method | Mass | Remarks |
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power density | 120 µW/cm² | - | - | - | - |
SAR | 548 mW/kg | - | calculated | - | - |
The data showed that the extent of DNA damage in mice which were pre-exposed to radiofrequency for 1 day and then subjected to gamma radiation was not significantly different from those animals exposed to gamma radiation alone. However, mice which were pre-exposed to radiofrequency for 3, 5, 7 and 14 days showed a progressively decreased DNA damage and the data were significantly different from those mice exposed to gamma radiation alone.
Thus, the findings indicate that radiofrequency pre-exposure is capable to induce an adaptive response and that the pre-exposure for more than 4 hours for 1 day is necessary to elicit such an adaptive response.
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