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

1.内向整流钾通道Kir4.1在螺旋神经节细胞周围的血管纹、支持细胞和卫星细胞中均有表达。KIR4.1在外沟细胞也有表达。这些结果提示，内向整流外沟细胞中的Kir4.1钾通道可能通过缝隙连接在钾离子循环机制中起重要作用。2.在BRN-4缺乏的情况下，耳蜗侧壁II型纤维细胞的Na，K-ATPase样免疫反应明显降低。间隙连接蛋白26在突变型耳蜗侧壁中的纤维细胞中分布稀疏。而Na，K-ATPase和电压门控性钾通道KCNQ1在该突变体的血管纹边缘细胞中大量表达。提示DFN3非综合征性聋耳蜗侧壁纤维细胞功能障碍和K+离子循环途径受阻可能是DFN3非综合征性耳聋的原因之一。3.在螺旋韧带的I型纤维细胞、II型纤维细胞和纤维上纤维细胞中均有较强的GLAST样免疫反应。谷氨酰胺合成酶在螺旋韧带的I型纤维细胞、II型纤维细胞、III型纤维细胞和纤维上皮细胞、血管纹的基底细胞中有丰富的表达。这些结果表明，耳蜗结缔组织细胞中丰富的GLAST和谷氨酰胺合成酶可能起到维持外淋巴液谷氨酸浓度在低(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.