Auteurs

Maskey D, Kim M, Aryal B, Pradhan J, Choi IY, Park KS, Son T, Hong SY, Kim SB, Kim HG, Kim MJ. Effect of 835 MHz radiofrequency radiation exposure on calcium binding proteins in the hippocampus of the mouse brain. Brain Res. Dec 4, 2009. Ahead of print.

Introduction
Ca2+ ion controls critical processes in the nervous system. Radiofrequency (RF) radiation may alter Ca2+ homeostasis. Changes in the expression of calcium binding proteins (CaBP), such as calbindin D28-k (CB) and calretinin (CR), may be indicative of such homeostatic changes.

Objective
The objective was to investigate whether 835 MHz RF radiation at different specific absorption rate (SAR) levels and exposure durations affected calbindin D28-k and calretinin in the mouse hippocampus.

Methods
Six-week-old male ICR mice were divided randomly into 6 groups of 10 animal each: Group A: control group, Group B: 1 hour per day at SAR=1.6 W/kg for 5 days, Group C: 1 hour per day at SAR=4.0 W/kg for 5 days, Group D: 5 hours of RF exposure for 1 day at SAR=1.6 W/kg, Group E: 5 hours of RF exposure for 1 day at SAR=4.0 W/kg, Group F: daily exposure for 1 month at SAR=1.6 W/kg. Calbindin D28-k  and calretinin expression were measured with immunohistochemistry. Image analysis was performed in each hippocampal region of cornu ammonis (CA1, CA3) and dentate gyrus.

Results
Calbindin D28-k immunoreactivity was uniformly distributed in all 6 groups. In all the groups, calbindin D28-k immunoreactivity was moderate in the cornu ammonis areas and more prominent in the dentate gyrus. Calretinin immunoreactivity revealed prominently stained pyramidal cells with dendrites running perpendicularly in the cornu ammonis area. Pyramidal cell loss was observed in the cornu ammonis 1 (CA1) area of the hippocampus after exposure for 1 month at SAR=1.6 W/kg (Group F).

Conclusion
The authors have concluded that 835 MHz RF radiation may be harmful and that its effects on Ca2+in human cerebrum should be tested.

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