Expression of voltage-gated potassium channels in the inner ear and herediatary deafness : molecular biological analysis

1.内整流钾通道Kir4.1在血管纹、耳蜗支持细胞和螺旋神经节细胞周围的卫星细胞中表达。Kir4.1也存在于外沟细胞中。这些结果表明，外沟细胞内整流的Kir4.1钾通道可能在通过间隙连接的钾离子循环机制中起重要作用。在brn -4缺失的情况下，耳蜗侧壁II型纤维细胞的Na、k - atp样免疫反应性明显降低。连接蛋白26在突变耳蜗侧壁的纤维细胞中稀疏分布。相比之下，Na、k - atp酶和电压门控钾通道KCNQ1在该突变体血管纹边缘细胞中大量表达。这些发现表明，耳蜗外侧壁纤维细胞功能障碍和通过间隙连接的K+离子循环通路中断可能导致人DFN3非综合征性耳聋的耳蜗内电位抑制和深度听力损失。在螺旋韧带的I型纤维细胞、II型纤维细胞和胃上纤维细胞中发现了强烈的glast样免疫反应。谷氨酰胺合成酶在螺旋韧带、血管纹基底细胞的I型纤维细胞、II型纤维细胞、III型纤维细胞和胃上纤维细胞中大量表达。这些结果表明，耳蜗结缔组织细胞中丰富的谷氨酰胺合成酶和谷氨酰胺合成酶可能起着维持淋巴周围谷氨酸浓度在低（无毒）水平的作用。

1.Inwardly rectifying potassium channel Kir4.1 was expressed in the stria vascularis, cochlear supporting cell and satellite cells surround spiral ganglion cells. Kir4.1 was also found in the outer sulcus cells. These results suggest that inwardly rectifying Kir4.1 potassium channel in the outer sulcus cells may play a important role in the potassium ion recycling mechanism via gap junctions.2.In the Brn-4-deficient, Na, K-ATPase-like immunoreactivity in the type II fibrocytes of the cochlear lateral wall was remarkably decreased. Connexin 26 was sparsely distributed among the fibrocytes in the mutant cochlear lateral wall. In contrast, Na, K-ATPase and voltage-gated potassium channel KCNQ1 were abundantly expressed in the marginal cells of the stria vascularis in this mutant. These findings suggest that a dysfunction of fibrocytes in the cochlear lateral wall and an interruption of the K+ ion recycling pathway via gap junctions may result in the depression of endocochlear potential and profound hearing loss in human DFN3 non-syndromic deafness.3.Intense GLAST-like immunoreactivity was found in the type I fibocytes, type II fibrocytes and the suprastrial fibrocytes in the spiral ligament. Glutamine synthetase was abundantly expressed in the type I fibrocytes, the type II fibrocytes, the type III fibrocytes and the suprastrial fibrocytes in the spiral ligament, the basal cells of the stria vascularis. These results suggest that abundant GLAST and glutamine synthetase in the connective tissue cells in the cochlea may function to maintain the perilymphatic glutamate concentration at a low (nontoxic) level.