Ischemia-reperfusion alters the immunolocalization of glial aquaporins in rat retina

Glial cells control the retinal osmohomeostasis, in part via mediation of water fluxes through aquaporin (AQP) water channels. By using immunohistochemical staining, we investigated whether ischemia-reperfusion of the rat retina causes alterations in the distribution of AQP1 and AQP4 proteins. Transient ischemia was induced in retinas of Long-Evans rats by elevation of the intraocular pressure for 60 min. In control retinas, immunoreactive AQP1 was expressed in the outer retina and by distinct amacrine cells, and AQP4 was expressed by glial cells (Müller cells and astrocytes) predominantly in the inner retina. After ischemia, retinal glial cells in the nerve fiber/ganglion cell layers strongly expressed AQP1. The perivascular staining around the superficial vessels altered from AQP4 in control retinas to AQP1 in postischemic retinas. The data suggest that the glial cell-mediated water transport in the retina is altered after ischemia especially at the superficial vessel plexus.