López-Escámez J A, Schacht J
Kresge Hearing Research Institute, University of Michigan, Ann Arbor 48109, USA.
Acta Otolaryngol. 1995 Nov;115(6):759-64. doi: 10.3109/00016489509139399.
Intracellular Ca2+([Ca2+]i) is elevated by depolarization or mechanical stimulation in some hair cell systems. It is not clear whether both these stimuli promote Ca2+ entry in mammalian vestibular hair cells. We monitored [Ca2+]i with the indicator fluo-3 in isolated type I vestibular hair cells of the guinea pig maintained in Hanks' balanced salt solution (HBSS). Mechanical stimulation by bolus application of HBSS led to an immediate rise of [Ca2+]i. The effect depended upon the presence of extracellular Ca2+([Ca2+]o) and no increase occurred in calcium-free HBSS supplemented with calcium-chelators. When the cells were depolarized by bolus application of KCl (final concentration, 100 mM KCl in modified HBSS), the increase in [Ca2+]i was similar to that elicited by HBSS. In the absence of [Ca2+]o, the application of KCI/HBSS led to a slow sustained increase in the fluorescence of the cells suggesting release of calcium from intracellular stores. Finally, treatment of cells with BAPTA prior to mechanical stimulation prevented the rise in [Ca2+]i indicating the need for intact stereociliary tip-links. The results are consistent with the hypothesis that mechanical stimulation elevates [Ca2+]i in isolated vestibular hair cells via calcium influx through mechanotransduction channels.
在一些毛细胞系统中，去极化或机械刺激会使细胞内钙离子浓度（[Ca2+]i）升高。目前尚不清楚这两种刺激是否都能促进钙离子进入哺乳动物前庭毛细胞。我们在 Hank's 平衡盐溶液（HBSS）中培养的豚鼠分离的 I 型前庭毛细胞中，用荧光指示剂 fluo-3 监测 [Ca2+]i。通过推注 HBSS 进行机械刺激会导致 [Ca2+]i 立即升高。这种效应取决于细胞外钙离子（[Ca2+]o）的存在，在添加了钙螯合剂的无钙 HBSS 中不会出现升高。当通过推注 KCl（最终浓度，在改良 HBSS 中为 100 mM KCl）使细胞去极化时，[Ca2+]i 的增加与 HBSS 引起的增加相似。在没有 [Ca2+]o 的情况下，应用 KCl/HBSS 会导致细胞荧光缓慢持续增加，表明钙离子从细胞内储存库中释放。最后，在机械刺激前用 BAPTA 处理细胞可防止 [Ca2+]i 升高，这表明需要完整的静纤毛顶端连接。这些结果与以下假设一致，即机械刺激通过机械转导通道的钙内流升高分离的前庭毛细胞中的 [Ca2+]i。
