Department of Otolaryngology, Faculty of Medicine, Kagawa University, Ikenobe 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan.
Institute of Neuroscience, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Kagawa, Japan.
Pflugers Arch. 2022 May;474(5):505-515. doi: 10.1007/s00424-021-02661-9. Epub 2022 Feb 3.
The endolymphatic sac is a small sac-shaped organ at the end of the membranous labyrinth of the inner ear. The endolymphatic sac absorbs the endolymph, in which the ion balance is crucial for inner ear homeostasis. Of the three sections of the endolymphatic sac, the intermediate portion is the center of endolymph absorption, particularly sodium transport, and is thought to be regulated by aldosterone. Disorders of the endolymphatic sac may cause an excess of endolymph (endolymphatic hydrops), a histological observation in Meniere's disease. A low-salt diet is an effective treatment for Meniere's disease, and is based on the assumption that the absorption of endolymph in the endolymphatic sac abates endolymphatic hydrops through a physiological increase in aldosterone level. However, the molecular basis of endolymph absorption in each portion of the endolymphatic sac is largely unknown because of difficulties in gene expression analysis, resulting from its small size and intricate structure. The present study combined reverse transcription-quantitative polymerase chain reaction and laser capture microdissection techniques to analyze the difference of gene expression of the aldosterone-controlled epithelial Na channel, thiazide-sensitive Na-Cl cotransporter, and Na, K-ATPase genes in the three individual portions of the endolymphatic sac in a rat model. A low-salt diet increased the expression of aldosterone-controlled ion transporters, particularly in the intermediate portion of the endolymphatic sac. Our findings will contribute to the understanding of the physiological function of the endolymphatic sac and the pathophysiology of Meniere's disease.
内淋巴管囊是内耳膜迷路末端的一个小囊状器官。内淋巴管囊吸收内淋巴，内淋巴中的离子平衡对内耳稳态至关重要。在内淋巴管囊中，三个部分的中间部分是内淋巴吸收的中心，特别是钠转运，并且被认为受醛固酮调节。内淋巴管囊的紊乱可能导致内淋巴过多（内淋巴积水），这是梅尼埃病的组织学观察结果。低盐饮食是梅尼埃病的有效治疗方法，其假设是内淋巴管囊中内淋巴的吸收通过醛固酮水平的生理增加来减轻内淋巴积水。然而，由于其体积小且结构复杂，内淋巴管囊中每个部分的内淋巴吸收的分子基础在很大程度上仍不清楚。本研究结合逆转录定量聚合酶链反应和激光捕获显微切割技术，分析了盐敏感 Na-Cl 共转运体和 Na，K-ATP 酶基因在醛固酮控制的上皮 Na 通道的基因表达差异在盐敏感大鼠模型的内淋巴管囊的三个独立部分。低盐饮食增加了醛固酮控制的离子转运体的表达，特别是在内淋巴管囊的中间部分。我们的发现将有助于理解内淋巴管囊的生理功能和梅尼埃病的病理生理学。
