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S. Hara, A. Hazama, Y. Sasaki, M. Dogru, K. Tsubota; The Effect of Topical Amiloride Eye Drops on Ocular Surface Tear Retention in Rabbits . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4399.
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Purpose:Epithelial sodium channels( ENaC) exist many epithelial cells, such as epitheliae of renal convoluted tubules, and are involved in the resorption of sodium and water into the epithelial cells. It is also known that ENaC are blocked and water resorption is suppressed by amiloride in the kidney. We investigated the expression of ENaC in human and rabbit conjunctival epithelial cells, and the effect of topical amiloride eye drops on ocular surface tear retention. Methods:We obtained both human conjunctival tissue during pterygium surgery from healthy flap site with informed consent and rabbit conjunctiva following the guidelines of the tenets of Helsinki. Immunohistochemistry staining in conjunctival samples was performed for the presence of ENaC. 0.1% amiloride eye drops were prepared by diluting the agent with sterile saline solution. Topical amiloride was applied once in 4 right eyes of 4 New Zealand rabbits and the left eyes were allocated to sterile saline solution applied at the same time. Schirmer test I was performed before, and 5,15,30 and 60 minutes after application of amiloride or saline drops in the excised tissues. Results:The existence of ENaC was confirmed both in human and rabbit conjunctival samples by immunohistochemical staining. Although the mean Schirmer test scores between left and right eyes of the rabbits did not differ from each other before application of eye drops, the mean Schirmer test values showed a dramatic time wise increase in rabbit eyes which received amiloride drops compared to the opposite eyes receiving saline drops. Schirmer test results increased by two fold at 15 minutes and the effect was maintained at one hour in eyes treated with amiloride drops. Conclusions:ENaC exist on rabbit and human conjunctival tissues. The increase of Schirmer test I scores after application of amiloride eye drops may be due to retention of secreted tears on the ocular surface through suppression of tear resorption from the conjunctiva.Topical amiloride may find potential applications in the treatment of dry eye syndromes.
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