Tolomeo J A, Steele C R, Holley M C
Department of Physiology, University of Bristol, England.
Biophys J. 1996 Jul;71(1):421-9. doi: 10.1016/S0006-3495(96)79244-5.
Mammalian auditory outer hair cells generate high-frequency mechanical forces that enhance sound-induced displacements of the basilar membrane within the inner ear. It has been proposed that the resulting cell deformation is directed along the longitudinal axis of the cell by the cortical cytoskeleton. We have tested this proposal by making direct mechanical measurements on outer hair cells. The resultant stiffness modulus along the axis of whole dissociated cells was 3 x 10(-3) N/m, consistent with previously published values. The resultant axial and circumferential stiffness moduli for the cortical lattice were 5 x 10(-4) N/m and 3 x 10(-3) N/m, respectively. Thus the cortical lattice is a highly orthotropic structure. Its axial stiffness is small compared with that of the intact cell, but its circumferential stiffness is within the same order of magnitude. These measurements support the theory that the cortical cytoskeleton directs electrically driven length changes along the longitudinal axis of the cell. The Young's modulus of the circumferential filamentous components of the lattice were calculated to be 1 x 10(7) N/m2. The axial cross-links, believed to be a form of spectrin, were calculated to have a Young's modulus of 3 x 10(6) N/m2. Based on the measured values for the lattice and intact cell cortex, an estimate for the resultant stiffness modulus of the plasma membrane was estimated to be on the order of 10(-3) N/m. Thus, the plasma membrane appears to be relatively stiff and may be the dominant contributor to the axial stiffness of the intact cell.
哺乳动物的听觉外毛细胞会产生高频机械力，增强内耳中基底膜的声音诱导位移。有人提出，由此产生的细胞变形是由皮质细胞骨架沿着细胞的纵轴引导的。我们通过对外毛细胞进行直接力学测量来验证这一观点。沿整个解离细胞轴的合成刚度模量为3×10⁻³ N/m，与先前发表的值一致。皮质晶格的轴向和周向合成刚度模量分别为5×10⁻⁴ N/m和3×10⁻³ N/m。因此，皮质晶格是一种高度正交各向异性的结构。与完整细胞相比，其轴向刚度较小，但其周向刚度在同一数量级内。这些测量结果支持了皮质细胞骨架沿着细胞纵轴引导电驱动长度变化的理论。晶格周向丝状成分的杨氏模量经计算为1×10⁷ N/m²。轴向交联（被认为是血影蛋白的一种形式）经计算其杨氏模量为3×10⁶ N/m²。根据晶格和完整细胞皮质的测量值，估计质膜的合成刚度模量约为10⁻³ N/m。因此，质膜似乎相对较硬，可能是完整细胞轴向刚度的主要贡献者。
