Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles, CA 90995-1624, USA.
Hear Res. 2012 Oct;292(1-2):64-70. doi: 10.1016/j.heares.2012.08.004. Epub 2012 Aug 24.
Auditory hair cells in the amphibian papilla (APHCs) of the leopard frog, Rana pipiens pipiens, have a significantly higher permeability to water than that observed in mammalian hair cells. The insensitivity of water permeability in frog hair cells to extracellular mercury suggests that an amphibian homologue of the water channel aquaporin-4 (AQP4) may mediate water transport in these cells. Using immunocytochemistry, we show that an AQP4-like protein is found in APHCs. Rabbit anti-AQP4 antibody was used in multiple-immunohistochemical staining experiments along with AP hair cell and hair bundle markers in leopard frog and mouse tissue. AQP4 immunoreactivity was found in the basal and apical poles of the APHCs and shows uniform immunoreactivity. This study provides the first identification and localization of an AQP4-like protein in the amphibian inner ear. We also report a more direct measure of hyperosmotically-induced volume changes in APHCs that confirms previous findings. The presence of water channels in anuran APHCs constitutes a novel physiological difference between amphibian and mammalian hair cell structure and function.
两栖类耳斑（APHCs）中的听觉毛细胞对水的通透性比哺乳动物毛细胞观察到的要高得多。青蛙毛细胞对细胞外汞的水通透性不敏感表明，水通道 aquaporin-4（AQP4）的两栖类同源物可能介导这些细胞中的水转运。通过免疫细胞化学，我们发现在 APHCs 中存在一种类似于 AQP4 的蛋白。兔抗 AQP4 抗体与 AP 毛细胞和毛束标记物一起用于豹蛙和小鼠组织的多次免疫组织化学染色实验。AQP4 免疫反应性存在于 APHCs 的基底和顶端极中，并显示均匀的免疫反应性。这项研究首次在两栖类内耳中鉴定和定位了一种类似于 AQP4 的蛋白。我们还报告了对 APHCs 中高渗诱导的体积变化的更直接测量，这证实了之前的发现。水通道在两栖类 APHCs 中的存在构成了两栖类和哺乳类毛细胞结构和功能之间的一种新的生理差异。
