Abstract
Purpose: :
Endothelin-1 (ET-1) is a vasoactive peptide which has gained prominence in recent years for its neurodegenerative role in glaucoma. ET-1 mediates some its neurodegenerative effects by its actions on the ETB receptor. The purpose of this study was to determine if there are changes in ETB receptor expression in vivo in the Morrison’s elevated intraocular pressure (IOP) model of glaucoma in rats.
Methods: :
IOP elevation was carried out in one eye of adult male Brown Norway rats using the Morrison’s method (by injection of hypertonic saline through the episcleral veins), while the contralateral eye served as control. Following intraocular pressure elevation, IOP was routinely monitored using the Tonolab tonometer. Following 2 to 4 weeks of IOP elevation, the rats were sacrificed. Retinal sections were obtained from control and IOP elevated rat eyes and analyzed for changes in ETB expression by immunohistochemistry. Another set of Brown Norway rats were subjected to the Morrison’s method of IOP elevation and retinal plasma membrane extracts were analyzed for ETB receptor expression by immunoblot analysis.
Results: :
IOP elevation for 2 weeks produced an increased in ETB receptor expression in the retinal ganglion cells, as determined by immunohistochemical analysis. A prominent increase in ETB receptor protein levels was also found in plasma membrane extracts from retinas of rats with IOP elevation
Conclusions: :
Increased intraocular pressure as seen in primary open angle glaucoma produces increased ETB receptor expression, which could contribute to apoptosis of retinal ganglion cells. Use of endothelin receptor antagonists could have neuroprotective effects in glaucoma.
Keywords: neuroprotection • ganglion cells • intraocular pressure