Functional significance of the gap junctions in the ion transport mechanism in the cochlea -molecular biological analysis

1.研究了Na，K-ATPase、Na-K-Cl共转运蛋白、连接蛋白26和连接蛋白31在小鼠耳蜗组织中的免疫组织化学定位。在螺旋韧带中的II型纤维细胞、血管纹中的肌上纤维细胞和边缘细胞中可见较强的Na，K-ATPase样免疫反应。Na-K-Cl共转运体的分布模式与Na，K-ATPase相似。连接蛋白26密集分布于螺旋韧带内的纤维细胞和血管纹的基底层细胞中。结论：1.连接蛋白31广泛分布于螺旋韧带的纤维细胞中。研究了Na，K-ATPase和连接蛋白26在小鼠耳蜗生后发育过程中的表达。Na，K-ATPase和Cx26在螺旋韧带内纤维细胞中的表达模式与内淋巴潜能的快速生长和成熟相吻合。在缺乏Brain-4的突变小鼠中，内淋巴电位显著降低。提示纤维细胞功能障碍和通过缝隙连接的跨细胞通路的中断可以导致该突变小鼠耳蜗内淋巴电位的抑制。外周淋巴灌流长链酒精导致内淋巴电位的抑制，这些结果有力地表明，通过缝隙连接的跨细胞途径在耳蜗内淋巴电位的产生中起着非常重要的作用。

1. Immunohistochemical localization of Na,K-ATPase, Na-K-Cl cotransporter, connexin 26 and connexin 31 in the mouse cochlea was studied in the present investigation. Intense Na,K-ATPase-like immunoreactivity was observed in the type II fibrocyte in the spiral ligament, suprastrial fibrocytes and marginal cells in the stria vascularis. The distribution pattern of Na-K-Cl cotransporter was comparable to that of Na,K-ATPase. Connexin 26 was densely distributed among the fibrocytes in the spiral ligament and along the basal cells of the stria vascularis. Connexin 31 was also widely distributed among the fibrocytes in the spiral ligament.2. The expression of Na,K-ATPase and connexin 26 was studied in the postnatal developmental process of the mouse cochlea. The expression patterns of Na,K-ATPase and connexin 26 in the fibrocytes in the spiral ligament coincided with the rapid growth and maturation of the endolymphatic potential.3. The endolymphatic potential was significantly decreased in the mutant mouse lacking Brain-4. It is suggested that a dysfunction of fibrocytes and an interruption of the transcellular route via gap junctions can cause a depression of endolymphatic potential in the cochlea of this mutant mouse.4. The perilymphatic perfusion of long-chain alcohol resulted in the depression of endolymphatic potential.These results obtained in the present study strongly suggest that the transcellular pathway via gap junctions plays a very important role in the generation of endolymphatic potential in the cochlea.