The Effect Of Glucocorticoid On AQP1 In Otitis Media With Effusion

Objective1. To develop a animal model for otitis media with effusion (OME).2. To explore the expression pattern of aquaporin 1(AQP1) in otitis media with effusion in guinea pigs, and the effect of glucocorticoid on AQP1.Methods1. In 22 guinea pigs, the left nasal orifice of eustachian tube was approached via a transpalatal incision and obstructed with polyvinyl acetal material. Then all ears were evaluated by otomicroscopy every day. On each of days 7, 14 and 21, six guinea pigs were killed for histologic study and exploration of material.2. Immunohistochemical stain was used to detect AQP1 in the middle ear of normal guinea pigs.3. 20 guinea pigs of OME model were equally divided into two groups: Dexa and OME. The latter group received dexamethasone 5mg/kg via intraperitoneal injection for seven days since the 7th day postoperatively. Bilateral bullae of 5 normal guinea pigs were dissected out. Then western blotting was used to detect the expression of AQP1 in three groups.Results1. Of the 22 guinea pigs entered into the study, 20 ears (90.9%) were found to have effusion 3-7days after operation. The epithelium initially developed a hyperplasia. And the submucosa showed vascular and lymphatic dilatations with inflammatory cell infiltration. None of the contralateral control ears had evidence of disease on otomicroscopic examination and histologic study.2. Immunohistochemical analysis showed that AQP1 was localized at capillary endothelial cells and fibroblasts in lamina propria mucosae. And the OME group tend to show a stronger and boarder signal of AQP1.3. Immunoblot analyses revealed that AQP1 were detected as 28kDa protein in the middle ear membrane of the guinea pigs. Immunoblot analyses revealed that there were significant differences in three groups. Quantitative analysis showed that AQP1 expression was highter in the Dexa group than in the OME group (t=2.733 P<0.05).Conclusion1. This experimental methods provoked reproducible pathologic signs similar to those for otitis media with effusion.2. AQP1 subtype is expressed in the middle ear cavity of guinea pigs and may play a vital role in the water homeostasis of the middle ear.3. Glucocorticoid could induce the expression of AQP1, which may be the mechanism of treatment for OME by Glucocorticoid.