The preventive effect of N-nitro L-arginine methyl ester in experimentally induced myringosclerosis

Objective: The purpose of this study was to investigate the antiinflammatory and antifibrotic effects of N-nitro L-arginine methyl ester (L-NAME) in experimentally induced myringosclerosis. Methods: Twenty Wistar albino rats were bilaterally myringotomized and divided randomly into four groups, each including five rats. Group I received no treatment, Group II was treated with topical saline solution, Group III received topical L-NAME and Group IV received intraperitoneally administered L-NAME. After 2 weeks, the tympanic membranes were examined and scored by otomicroscopy regarding the extent of the myringosclerosis. Then the tympanic membranes were harvested and evaluated histopathologically by light microscopy. The intensity of inflammation and degree of myringosclerosis were evaluated, the mean thickness of tympanic membranes were also measured. Results: The tympanic membranes of Groups I and II showed extensive myringosclerosis in contrast to those of Groups III and IV which had significantly less or no changes (p < 0.05). The inflammation and fibroblastic activity of the lamina propria in the tympanic membranes of Groups III and IV were found to be significantly less pronounced (p < 0.05). The tympanic membranes were found to be significantly thicker in Groups I and II when compared with Groups III and IV (p < 0.05). Conclusion: Our results showed that both topical and intraperitoneal applications of L-NAME supressed inflammation, reduced fibroblastic proliferation and decreased the formation of myringosclerosis in myringotomized rat tympanic membranes. (C) 2011 Elsevier Ireland Ltd. All rights reserved.