Wu M, Santos-Sacchi J
Sections of Otolaryngology and Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
J Membr Biol. 1998 Nov 15;166(2):111-8. doi: 10.1007/s002329900453.
The outer hair cell (OHC) from the mammalian organ of Corti possesses a bell-shaped voltage-dependent capacitance function. The nonlinear capacitance reflects the activity of membrane bound voltage sensors associated with membrane motors that control OHC length. We have studied the effects of the lipophilic ions, tetraphenylborate (TPB-) and tetraphenylphosphonium (TPP+), on nonlinear capacitance and motility of isolated guinea-pig OHCs. Effects on supporting cells were also investigated. TPB- produced an increase in the peak capacitance (Cmpk) and shifted the voltage at peak capacitance (VpkCm) to hyperpolarized levels. Washout reversed the effects. Perfusion of 0.4 micrometer TPB- caused an average increase in Cmpk of 16.3 pF and VpkCm shift of 13.6 mV. TPP+, on the other hand, only shifted VpkCm in the positive direction, with no change in Cmpk. The contributions from native OHC and TPB--induced capacitance were dissected by a double Boltzmann fitting paradigm, and by blocking native OHC capacitance. While mechanical response studies indicate little effect of TPB- on the motility of OHCs which were in normal condition or treated with salicylate or gadolinium, the voltage at maximum mechanical gain (VdeltaLmax) was shifted in correspondence with native VpkCm, and both changed in a concentration-dependent manner. Both TPB--induced changes in Cmpk and VpkCm were affected by voltage prepulses and intracellular turgor pressure. TPB- induced a voltage-dependent capacitance in supporting cells whose characteristics were similar to those of the OHC, but no indication of mechanical responses was noted. Our results indicate that OHC mechanical responses are not simply related to quantity of nonspecific nonlinear charge moved within the membrane, but to the effects of motility voltage-sensor charge movement functionally coupled to a mechanical effector.
哺乳动物柯蒂氏器中的外毛细胞（OHC）具有钟形的电压依赖性电容功能。非线性电容反映了与控制OHC长度的膜马达相关的膜结合电压传感器的活性。我们研究了亲脂性离子四苯硼酸盐（TPB-）和四苯鏻（TPP+）对分离的豚鼠OHC非线性电容和运动性的影响。还研究了它们对支持细胞的影响。TPB-使峰值电容（Cmpk）增加，并使峰值电容时的电压（VpkCm）向超极化水平移动。洗脱可逆转这些效应。灌注0.4微米的TPB-导致Cmpk平均增加16.3 pF，VpkCm偏移13.6 mV。另一方面，TPP+仅使VpkCm向正向移动，而Cmpk无变化。通过双玻尔兹曼拟合范式以及阻断天然OHC电容，剖析了天然OHC和TPB-诱导电容的贡献。虽然机械反应研究表明TPB-对处于正常状态或用阿司匹林或钆处理的OHC的运动性影响很小，但最大机械增益时的电压（VdeltaLmax）与天然VpkCm相应地发生了偏移，并且两者均以浓度依赖性方式变化。TPB-诱导的Cmpk和VpkCm的变化均受电压预脉冲和细胞内膨压影响。TPB-在支持细胞中诱导出一种电压依赖性电容，其特征与OHC相似，但未观察到机械反应的迹象。我们的结果表明，OHC的机械反应并非简单地与膜内非特异性非线性电荷的数量相关，而是与功能上耦合到机械效应器的运动电压传感器电荷运动的影响相关。
