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B.M. Junghans, M. Goodyear, D. Crewther, S.G. Crewther; A Role for Aquaporin–4 in the Induction of Form–Deprivation Myopia . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3344.
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Purpose: Aquaporins (AQP) are transmembrane proteins that function as water channels within cells. Roles for AQP4 in neural signaling have been suggested. In the neural retina, AQP4 is typically found colocalized with Kir4.1 potassium channels on Muller cells and has been postulated to play a role in rapid cellular water movements accompanying light–dark transduction (Verkman Exp Eye Res. 76 (2003) 137–143). We hypothesize that the distribution of AQP4 expression should be affected during induction of form deprivation myopia (FDM) in chick, as significant volumetric changes occur in two main fluid reservoirs of the eye, namely the vitreous chamber and the choroidal lymphatics. Methods: Thirteen chickens were raised from Day 2 with monocular translucent occluders which were removed after 48, 72, 84, 96 or 120 hours. Retinoscopy to determine refractive error and ultrasonography for axial length were performed prior to sacrifice. Eyes were cryosectioned to produce transverse sections of retina, choroid and sclera for immunohistochemistry using rabbit polyclonal AQP4 primary antibodies and fluorescent secondary antibodies. Results: Analyses revealed enhanced expression of AQP4 at the ganglion cell layer and inner plexiform layer as early as 48 hours after FD began, when significant myopia was already present. This continued until 120 hours. Conclusions: These results suggests that AQP4 channels on Muller cells may play a role in the morphological changes seen during the induction of FDM by regulating water permeability and K+ transport across the retina between the choroid and the vitreous chamber.
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