Bechem M, Glitsch H G, Pott L
Pflugers Arch. 1983 Nov;399(3):186-93. doi: 10.1007/BF00656713.
Single channel outward current fluctuations are recorded in excised (outside-out) membrane patches of isolated atrial cells in culture (cardioballs) from hearts of adult guinea-pigs. The ionic channel displays a high selectivity to K ions. Accordingly the reversal potential of the single channel current is close to the K equilibrium potential. The open channel conductance is unaffected by the membrane potential but depends on the K concentration of the outside solution (19.7pS at 2 mM Ko to 30.7pS at 20 mM Ko). The open state probability (Po) of the channel shows a marked voltage dependence. Po amounts to c.0.9 at -40 mV and decreases to c.0.1 at +40 mV. Under the assumption of no channel interaction a macroscopic steady state current voltage relationship is reconstructed from the single channel data. The relationship displays inward-going rectification. The rectification is due to the voltage dependence of Po. The I-V curve displays a negative slope at membrane potentials positive to -15 mV. In bathing solutions containing Ba ions (0.2 mM) Po is reduced by rapid closures which interrupt the open state events. The unit channel conductance is unaffected by Ba ions. The channel block exerted by Ba ions is augmented with increasing membrane hyperpolarization. The results suggest that the channel studied may represent a background K conductance.
在成年豚鼠心脏培养的分离心房细胞（心肌球）的切除（外向型）膜片中记录单通道外向电流波动。该离子通道对钾离子具有高度选择性。因此，单通道电流的反转电位接近钾平衡电位。开放通道电导不受膜电位影响，但取决于外部溶液的钾浓度（在2 mM钾离子浓度下为19.7 pS，在20 mM钾离子浓度下为30.7 pS）。通道的开放状态概率（Po）表现出明显的电压依赖性。在-40 mV时，Po约为0.9，在+40 mV时降至约0.1。在无通道相互作用的假设下，从单通道数据重建宏观稳态电流电压关系。该关系表现出内向整流。整流是由于Po的电压依赖性。在膜电位高于-15 mV时，I-V曲线呈现负斜率。在含有钡离子（0.2 mM）的浴液中，Po因快速关闭而降低，这些关闭中断了开放状态事件。单位通道电导不受钡离子影响。钡离子施加的通道阻断随着膜超极化的增加而增强。结果表明，所研究的通道可能代表一种背景钾电导。
