Holley M C, Ashmore J F
Department of Physiology, The Medical School, Bristol, UK.
Proc R Soc Lond B Biol Sci. 1988 Jan 22;232(1269):413-29. doi: 10.1098/rspb.1988.0004.
Isolated mammalian outer hair cells elongate or shorten respectively by several micrometres when electrically hyperpolarized or depolarized. The experiments in this paper were designed to locate the force-generating mechanism that drives length changes in outer hair cells, and to determine some of its basic properties. The whole-cell mode of the patch-clamp technique was used to stimulate cells electrically and to perfuse them with specific drugs. The pattern of displacement of cellular organelles, and the relative displacements of the cell base and apex during electrical stimulation with the cell mechanically anchored at various points along its length, suggest that the force-generating mechanism is distributed throughout the length of the cell. Further experiments altering the shape, volume and intracellular pressure of outer hair cells suggest that the mechanism is closely associated with the plasma membrane. These experiments also demonstrate that the characteristic tubular shape of outer hair cells is maintained by membrane-associated structures with elastic properties that enable the cell to return to its original shape after deformation. The mechanism controlling length changes may, therefore, be composed of two elements in parallel, namely a force generating element and a passive elastic element. Inhibitors of ATP synthesis, or the presence of the non-hydrolysable ATP analogue AMP.PNP, perfused into outer hair cells, failed to inhibit length changes. Drugs against actin, including phalloidin, cytochalasin B and cytochalasin D, and against tubulin, including colchicine, nocodazole and colcemid, also failed to inhibit length changes. We conclude that the force-generating mechanism is, therefore, unlike most other forms of cell motility, and possible alternative hypotheses are briefly discussed.
分离的哺乳动物外毛细胞在发生电超极化或去极化时，会分别伸长或缩短几微米。本文中的实验旨在确定驱动外毛细胞长度变化的力产生机制，并确定其一些基本特性。采用膜片钳技术的全细胞模式对细胞进行电刺激并用特定药物灌注。细胞器的位移模式，以及在细胞沿其长度的不同点进行机械固定时电刺激期间细胞基部和顶端的相对位移，表明力产生机制分布在细胞的整个长度上。改变外毛细胞形状、体积和细胞内压力的进一步实验表明，该机制与质膜密切相关。这些实验还表明，外毛细胞特有的管状形状由具有弹性特性的膜相关结构维持，使细胞在变形后能够恢复到其原始形状。因此，控制长度变化的机制可能由两个并行的元件组成，即力产生元件和被动弹性元件。灌注到外毛细胞中的ATP合成抑制剂或不可水解的ATP类似物AMP.PNP的存在，均未能抑制长度变化。针对肌动蛋白的药物，包括鬼笔环肽、细胞松弛素B和细胞松弛素D，以及针对微管蛋白的药物，包括秋水仙碱、诺考达唑和秋水仙酰胺，也未能抑制长度变化。我们得出结论，因此，力产生机制与大多数其他形式的细胞运动不同，并简要讨论了可能的替代假设。
