Analysis of the potassium ion recycling mechanism in the cochlea : a challenge for the better understanding of the inner ear dysfunction

在哺乳动物内耳中，存在两个独立的间隙连接系统，上皮细胞间隙连接系统和结缔组织细胞间隙连接系统。钾离子在哺乳动物耳蜗的机械电转导过程中起着关键作用，通过这两个间隙连接系统进行再循环。在哺乳动物内耳中已经报道了四种不同的连接蛋白，包括连接蛋白26、30、31和43。连接蛋白26、30和43分布于上皮细胞和结缔组织细胞间隙连接系统中。相反，连接蛋白31定位于结缔组织细胞间隙连接系统。在目前的调查中，我们已经表明，强烈的电压门控钾通道Kv3.1b亚基样免疫反应被发现在I型，III型和IV型纤维细胞的螺旋韧带。耳蜗外侧壁纤维细胞内存在电压门控性钾通道（Kv3.1b），该通道可能控制细胞内电位，在调节钾离子再循环机制中起重要作用。还研究了豚鼠耳蜗中内向整流Kir4.1钾通道的免疫组织化学定位。耳蜗Kir4.1钾通道可能在钾循环通路中起重要作用。为了阐明哺乳动物内耳中钾离子再循环的详细机制，需要进一步的研究。

In the mammalian inner ear, there are two independent gap junction systems, the epithelial cell gap junction system and the connective tissue cell gap junction system. Potassium ions, which play a pivotal role in the mechanoelectrical transduction process in the mammalian cochlea, are recycled via these two gap junction systems. Four different connexins, including connexin 26, 30, 31, and 43, have been reported in the mammalian inner ear. Connexin 26, 30, and 43 are distributed in both epithelial and connective tissue cell gap junction systems. In contrast, connexin 31 is localized to the connective tissue cells gap junction system. In the present investigation, we have shown that intense voltage-gated potassium channel Kv3.1b subunit-like immunoreactivity is found in the type I, type III, and type IV fibrocytes in the spiral ligament. Voltage-gated potassium channel, containing Kv3.1b, in the fibrocytes of the cochlear lateral wall may control the intracellular potential and play an important role in regulating the potassium ion recycling mechanism. Immunohistochemical localizations of inwardly rectifying Kir4.1 potassium channels were also studied in the guinea pig cochlea. Kir4.1 potassium channel in the cochlea may play an important role in the K+ recycling pathway. Further investigations are needed in order to elucidate the detailed potassium ion recycling mechanism in the mammalian inner ear.