Expression of an inwardly rectifying K+ channel, Kir5.1, in specific types of fibrocytes in the cochlear lateral wall suggests its functional importance in the establishment of endocochlear potential
Expression of an inwardly rectifying K+ channel, Kir5.1, in specific types of fibrocytes in the cochlear lateral wall suggests its functional importance in the establishment of endocochlear potential
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DOI：
10.1111/j.1460-9568.2004.03092.x
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发表时间：
2004-01-01
影响因子：
3.4
通讯作者：
Kurachi, Y
中科院分区：
文献类型：
--
作者：
Hibino, H;Higashi-Shingai, K;Kurachi, Y
耳蜗内淋巴含有150毫米的钾离子，具有大约+80毫伏的高电位。内淋巴的特殊离子组成和高电位对听力至关重要，并通过耳蜗外壁从淋巴周围到内淋巴的K+循环维持。Kir4.1、KCNQ1/KCNE1等多种K+通道表达于外壁血管纹，在K+循环中发挥重要作用。在这项研究中，我们检查了另一种K+通道Kir5.1的分布，发现它在耳蜗侧壁螺旋韧带中特异性表达。在直接参与K+循环的韧带和螺旋缘的II型、IV型和V型纤维细胞中检测到Kir5.1的特异性免疫反应性。Kir5.1在I型和III型纤维细胞中均未发现。虽然Kir5.1与Kir4.1在肾上皮细胞和视网膜Muller细胞中组装形成功能性的Kir通道，但双免疫标记显示它们在耳蜗侧壁的不同区域表达，即Kir4.1仅在血管纹中表达，而Kir5.1在螺旋韧带中表达。在发育过程中，Kir5.1亚基的表达开始明显晚于Kir4.1，并与耳蜗电位（EP）升高的“快速”阶段相关。因此，Kir5.1和Kir4.1通道亚基可能在耳蜗侧壁的K+循环中发挥不同的功能作用。
Cochlear endolymph contains 150 mm K+ and has a highly positive potential of approximate to+80 mV. The specialized ionic composition and high potential in endolymph are essential for hearing and maintained by circulation of K+ from perilymph to endolymph through the cochlear lateral wall. Various types of K+ channel such as Kir4.1 and KCNQ1/KCNE1 are expressed in stria vascularis of the lateral wall and play essential roles in K+ circulation. In this study, we examined a distribution of another K+ channel, Kir5.1, and found it specifically expressed in the spiral ligament of the cochlear lateral wall. Specific immunoreactivity for Kir5.1 was detected in type II, IV and V fibrocytes of the ligament and spiral limbus, all of which are directly involved in K+ circulation. Kir5.1 was not found in either type I or III fibrocytes. Although Kir5.1 assembles with Kir4.1 to form a functional Kir channel in renal epithelia and retinal Muller cells, double-immunolabelling revealed that they were expressed in distinct regions in the cochlea lateral wall, i.e. Kir4.1 only in stria vascularis vs. Kir5.1 in spiral ligament. During development, the expression of Kir5.1 subunits started significantly later than Kir4.1 and was correlated with the 'rapid' phase of the elevation of endocochlear potential (EP). Kir5.1 and Kir4.1 channel-subunits may therefore play distinct functional roles in K+ circulation in the cochlear lateral wall.