Gastric type H+, K+-ATPase in the cochlear lateral wall is critically involved in formation of the endocochlear potential
Gastric type H+, K+-ATPase in the cochlear lateral wall is critically involved in formation of the endocochlear potential
复制标题
DOI：
10.1152/ajpcell.00266.2006
复制
发表时间：
2006-11-01
影响因子：
5.5
通讯作者：
Kurachi, Yoshihisa
中科院分区：
文献类型：
--
作者：
Shibata, Toshiaki;Hibino, Hiroshi;Kurachi, Yoshihisa
耳蜗内淋巴具有大约 + 80 mV 的高正电位，称为耳蜗内电位 (EP)。 EP 对于听力至关重要，由通过耳蜗侧壁从外淋巴到内淋巴的 K+ 循环维持。各种 K+ 转运装置，例如 Na+、K+-ATP 酶、Na+-K+-2Cl(-) 协同转运蛋白以及 K+ 通道 Kir4.1 和 KCNQ1/KCNE1 在侧壁中表达，已知在耳蜗 K+ 循环中发挥不可或缺的作用。胃型 H+、K+-ATP 酶也显示在耳蜗侧壁中表达（Lecain E、Robert JC、Thomas A 和 Tran Ba Huy P. Hear Res 149：147-154，2000），但其功能作用尚未得到充分研究。在这项研究中，我们检查了 H+、K+-ATP 酶在耳蜗中的精确定位及其在 EP 形成中的参与。 RT-PCR分析表明，耳蜗表达胃α(1)-的mRNA，但不表达结肠α(2)-和H+、K+-ATPase的β-亚基。在分布于侧壁螺旋韧带和螺旋缘的 II、IV 和 V 型纤维细胞中检测到对 α1 亚基特异的抗体的免疫标记。在血管纹中也发现了强烈的免疫反应性。免疫电镜检查显示H+、K+-ATP酶仅位于纹状体边缘细胞的基底外侧部位。 Sch-28080（胃H+、K+-ATP酶的特异性抑制剂）应用于螺旋韧带以及血管纹导致EP显着减少。这些结果可能意味着耳蜗侧壁中的 H+、K+-ATP 酶对于 K+ 循环至关重要，因此在 EP 的生成中发挥着关键作用。
Cochlear endolymph has a highly positive potential of approximately + 80 mV known as the endocochlear potential (EP). The EP is essential for hearing and is maintained by K+ circulation from perilymph to endolymph through the cochlear lateral wall. Various K+ transport apparatuses such as the Na+, K+-ATPase, the Na+-K+-2Cl(-) cotransporter, and the K+ channels Kir4.1 and KCNQ1/KCNE1 are expressed in the lateral wall and are known to play indispensable roles in cochlear K+ circulation. The gastric type of the H+, K+-ATPase was also shown to be expressed in the cochlear lateral wall (Lecain E, Robert JC, Thomas A, and Tran Ba Huy P. Hear Res 149: 147-154, 2000), but its functional role has not been well studied. In this study we examined the precise localization of H+, K+-ATPase in the cochlea and its involvement in formation of EP. RT-PCR analysis showed that the cochlea expressed mRNAs of gastric alpha(1)-, but not colonic alpha(2)-, and beta-subunits of H+, K+-ATPase. Immunolabeling of an antibody specific to the alpha 1 subunit was detected in type II, IV, and V fibrocytes distributed in the spiral ligament of the lateral wall and in the spiral limbus. Strong immunoreactivity was also found in the stria vascularis. Immunoelectron microscopic examination exhibited that the H+, K+-ATPase was localized exclusively at the basolateral site of strial marginal cells. Application of Sch-28080, a specific inhibitor of gastric H+, K+-ATPase, to the spiral ligament as well as to the stria vascularis caused prominent reduction of EP. These results may imply that the H+, K+-ATPase in the cochlear lateral wall is crucial for K+ circulation and thus plays a critical role in generation of EP.