ENDOTHELIN A RECEPTOR EXPRESSION IN RAT MODEL OF OCULAR HYPERTENSION

Purpose: The endothelin system of peptides and their receptors have been implicated for their neurodegenerative role in glaucoma. The purpose of this study was to determine changes in ETA receptor expression in the retina in the Morrison's elevated IOP model of glaucoma in rats. Methods: IOP was elevated in the left eye of adult male retired breeder Brown Norway rats using the Morrison's model of glaucoma (by injection of hypertonic saline through episcleral veins) while the contralateral eye served as the corresponding control. The rats were maintained for two weeks following IOP elevation and sacrificed. Retinal sections were obtained from both the control and IOP-elevated eyes and analyzed for changes in ETA receptor expression using immunohistochemistry. ETA receptor immunostaining was co-localized with β-III-Tubulin, which is selectively expressed in retinal ganglion cells. Results: Rat eyes with IOP elevation showed an increase in immunostaining ETA receptor in several retinal layers including retinal ganglion cells, the inner plexiform layer, and the outer plexiform layer. An increased co-immunostaining of ETA receptors with β-III-Tubulin was observed both in retinal ganglion cells and inner plexiform layer. Conclusions: Elevated intraocular pressure results in an increase in ETA receptor expression. Increased endothelin receptor expression is associated with neurodegeneration in glaucoma.