豚鼠耳蜗单离外毛细胞的外向整流钾电流

Outwardly rectifying potassium currents in isolated outer hair cells in cochlea of guinea pig

目的 :观察豚鼠耳蜗单离外毛细胞 (OHC)的电生理特性 ,记录不同长度OHC的外向整流钾电流 ,分析区分外向整流钾电流所包含的通道电流成分 ,研究外向整流钾电流的动力学特征。方法 :采用酶消化法及机械分离OHC。运用全细胞膜片钳技术 ,在电压钳下记录K+ 通道电流。结果 :OHC的全细胞膜电容为 (30 .96±2 .79) pF(n =2 9) ,零电流电位 (30± 2 .1)mV(n =16 ) ,反转电位为 (- 5 1.6 7± 1.84 )mV(n =9)。不同长度OHC的外向整流钾电流存在系统差异 ,短OHC表现出大的钾电导 ,长OHC则相反。 10 0 μmol/L的氯化镉 (Cd Cl2 )抑制了OHC外向整流钾电流的最大电流幅度的 6 0 % ,且改变了电流的动力学特征 ,对峰电流的影响明显大于稳态电流 (P<0 .0 1,n =5 ) ;1mmol/L的四氨基吡啶 (4 AP)抑制了最大电流幅度的 4 3% ,没有改变电流的动力学特征。外向整流钾电流的激活符合Boltzmann方程 ,V1/ 2 =(- 11.0 7± 0 .2 6 )mV ,S =(6 .6 2± 1.74 )mV(n=13)。结论 :外向整流钾电流包含有钙离子激活的钾离子电流。

Objective: The purpose of this study was to investigate electrophysiological properties of isolated outer hair cells (OHCs) from cochlea of the guinea pig, record outwardly rectifying potassium currents in OHCs with different length, analyze component of outwardly rectifying potassium currents, study kinetics of the currents.Method:The whole cell patch clamp technique was used.Result:Whole cell capacitance of the OHC was ( 30.96 ± 2.79 )pF(n=29), zero current potential was (30± 2.1 )mV(n=16)and reversal potential was (- 51.67 ± 1.84 )mV(n=9). Variation in expression of outwardly rectifying potassium currents was found in OHCs with different length, namely, potassium conductance was greater in short OHC than in tall OHC. The maximal amplitude of outwardly rectifying potassium currents were reduced by 60% in the presence of 100 μmol/L CdCl 2 and change the kinetics of the currents, effects of CdCl 2 on the peak currents were greater when compared to the effects on the steady state currents (P< 0.01 ,n=5).1 mmol/L 4 aminopyridine (4 AP) inhibited 43% of the maximal amplitude of the currents and had no effect on the kinetics of the currents. Activation of the currents was described by Boltzmann equation, V 1/2 =(- 11.07 ± 0.26 )mV,S=( 6.62 ± 1.74 )mV(n=13).Conclusion:Outwardly rectifying potassium currents were composed of calcium activated potassium current, outward delayed rectifier potassium current and A type current.