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

哺乳动物内耳存在两个独立的缝隙连接系统，即上皮细胞缝隙连接系统和结缔组织细胞缝隙连接系统。钾离子在哺乳动物耳蜗机电信号转导过程中起着关键作用，它通过这两个缝隙连接系统进行循环。在哺乳动物的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分布在上皮细胞和结缔组织细胞缝隙连接系统中。相反，连接蛋白31定位于结缔组织细胞缝隙连接系统。在本研究中，我们发现在螺旋韧带的I型、III型和IV型纤维细胞中存在强烈的电压门控性钾通道Kv3.1b亚基样免疫反应。耳蜗侧壁肌纤维细胞中含有Kv3.1b的电压门控性钾通道可能控制细胞内电位，在调节钾离子循环机制中发挥重要作用。本文还研究了内向整流钾通道Kir4.1在豚鼠耳蜗内的免疫组织化学定位。耳蜗钾通道KIR4.1可能在K+循环途径中起重要作用。为了阐明哺乳动物内耳中钾离子循环的详细机制，还需要进一步的研究。

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.