Finnie JW, Chidlow G, Blumbergs PC, Manavis J, Cai Z. (2009). Heat shock protein induction in fetal mouse brain as a measure of stress after whole of gestation exposure to mobile telephony radiofrequency fields. Pathology. 41(3):276-9.
Assessment of the stress response in fetal mouse (a developing brain) after whole gestational exposure to radiofrequency fields.
Developing brains are more sensitive to radiofrequency originating from mobile telephony. Individual exposure to mobile phone microwaves in utero is now widespread as those devices became very integrated in the daily life.
The aim of the current study was to assess the stress response by measuring brain heat shock proteins (HSPs) to the insult induced by exposure to radiofrequency fields.
Pregnant Balb/c mice were exposed to whole body exposure of 4 W/kg of far-field radiofrequency for 60 minutes from gestation day 1 (E1) to gestation day 19 (E19). At E19, just prior to parturition, pregnant mice were anaesthetized, the fetuses rapidly collected, brains removed and immediately immersed in 4% paraformaldehyde. A total of 10 pregnant animals were exposed and one fetal brain selected from each pregnant female (n¼10) for neuropathological examination, the litter size in this strain usually ranging from six to ten. A pregnant sham-exposed group (n¼10) and a non-exposed, freely moving, cage control group (n¼10) without handling or further confinement were selected in the same manner. The stress was assessed by measurement of HSPs in the nervous system. These proteins are induced in many pathological conditions such as ischameia, degenerative diseases, epilepsy and trauma. Brain tissues from exposed and control mice were subjected to immunostaining to detect HSPs. Three types of HSP were studied: HSP32, HSP70, and HSP25. The 3 HSPs examined in the current study encompass the three most widely studied inducible members of the HSP family.
There was no induction of HSPs in all brains from the 3 groups. However, HSP25 immunoreactivity was consistently found and confined to certain regions of the brains in level 3 of exposed and non-exposed brains. Those served as positive control.
Discussion and Conclusions
The present study did not show an increased expression of HSPs in the brains of mice exposed to high-frequency fields from E1-E19 of the gestation period. This result is consistent with previous findings from published studies. The negative results in the current study was not related to inability of the method to detect HSPs since those proteins were detected in some nuclei in brains exposed to thermal stress (as positive control). It is possible that heat shock protein induction occurred in exposed fetal brains prior to E19 and was not detected by the current study since their up-regulation is transient, even if the stressor is applied over a protracted period. Furthermore, heat shock protein families show varying, but often overlapping, patterns of expression in different regions of the developing nervous system, suggesting specific functions at different stages of neural maturation.