The role of vasopressin to the formation of endolymphatic hydrops

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Recently, many lines of evidence have supported the possibilities that vasopressin (VP) has important role in the formation of endolymphatic hydrops in Meniere's disease. The aim of this study is to investigate the role of VP about endolymphatic hydrops. In this study, we examined two experiments. First, we examined whether or not the chronic administration of VP induce endolymphatic hydrops. Second, we investigated the expression pattern of vasopressin receptor (V2 receptor) and V2 specific water channel (aquaporin 2, AQP2).(1) VP was administered to the guinea pigs at the rats of 0.2U/kg/min, 0.4U/kg/min, 1U/kg/min fo 7days. The degree of hydrops was quatitatively assessed by increase ratio of the scala media area in the mid-modiolar sections of the cochlea. Scala media area of 0.4 and 1U/kg/min group was significantly increased compared with control group. We confirmed the high level of VP induce endolymphatic hydrops in the guinea pig.(2) We investigated the expression of V2 receptor and AQP2 mRNA via RT-PCR.The rat cochlea and endolymphatic sac were used. RT-PCR was done by specific primers for V2 receptor and AQP2. PCR products were electrophorased by agarose gel and sequenced. AQP2 and V2 receptor were both expressed in the rat cochlea and endolymphatic sac. These results indicate that vasopressin has important role for water regulation in the inner ear.In conclusion, all data from these experiments support that VP is closely linked to endolymphatic hydrops in Meniere's disease