Abstract
Abstract: :
Purpose: The development of retinal edema is a common complication of various ischemic and inflammatory ocular diseases. Fluid movements through the retinal tissue are facilitated by aquaporin (AQP) water channels expressed in plasma membranes of glial and neuronal cells. It is known that the retina of the rat express AQP4 and AQP1 water channel proteins while a possible expression of other members of the aquaporin protein family is unknown. We carried out RT–PCR and immunohistochemical studies to reveal the mRNA and protein expression of various aquaporins in the rat retina. Methods: Transient retinal ischemia was induced in one eye of adult rats by elevating the intraocular pressure for 60 minutes. Total RNA was isolated and analyzed by RT–PCR. Retinal slices were immunostained against various aquaporin proteins. Results: The sensory retina of the rat express mRNA for a diversity of aquaporins, including AQPs0,1,3,4,5,6,7,8,9, and 11. The mRNA for AQP2 remained under the detection level of the method used. AQP1 immunoreactivity is expressed by the outer retina and by single amacrine cells. AQP2 immunoreactivity was found at low level in horizontal cells. AQP4 immunoreactivity is strongly expressed in perivascular membranes and at the inner limiting membrane, as well as in the plexiform layers. AQP5 immunoreactivity was found diffusely distributed above the whole retinal tissue. AQP9 immunoreactivity is expressed by single amacrine cells. Conclusions: The retina of the rat express mRNAs for a diversity of different water channel proteins, suggesting that the retinal water homeostasis is mediated by the cooperation of different aquaporins. The functional significance of the various aquaporin proteins for neuronal activity and in pathophysiological conditions remains to be determined.
Keywords: ischemia • retina • gene/expression