Aquaporins are a family of small hydrophobic membrane proteins that serve as a selective pore through which water traverses the plasma membrane of different cell types. Aquaporin-4 is up-regulated in cerebral oedema of vasogenic type where there is increased blood-brain barrier permeability. The authors immunostained brains for aquaporin-4, which had previously been used in vascular tracer studies with albumin (Finnie et al. 2001, Finnie et al. 2002, and Finnie and Blumbergs 2004).
10 mice were acutely exposed, 10 mice were long-term exposed, 20 mice were sham-exposed and 20 mice were cage control animals (10 for each exposure condition). A positive control group was given a clostridial toxin known to cause microvascular endothelial injury, severe vasogenic oedema and up-regulation of aquaporin-4.
There was no increase in aquaporin-4 expression in mouse brains exposed to mobile phone microwaves compared to controls (sham exposure and cage control) brains after short or long-term exposure, while aquaporin-4 was substantially upregulated in the brains of mice given the clostridial toxin.
The authors conclude that brains exposed to mobile phone radiofrequency fields for a short or long duration did not show any immunohistochemically detectable up-regulation of the water channel protein, aquaporin-4, suggesting that there was no significant increase in blood-brain barrier permeability.