Gallin E K
Biophys J. 1984 Dec;46(6):821-5. doi: 10.1016/S0006-3495(84)84080-1.
Single calcium-activated potassium channel currents were recorded in intact and excised membrane patches from cultured human macrophages. Channel conductance was 240 pS in symmetrical 145 mM K+ and 130 pS in 5 mM external K+. Lower conductance current fluctuations (40% of the larger channels) with the same reversal potential as the higher conductance channels were noted in some patches. Ion substitution experiments indicated that the channel is permeable to potassium and relatively impermeable to sodium. The frequency of channel opening increased with depolarization and intracellular calcium concentration. At 10(-7) M (Ca++)i, channel activity was evident only at potentials of +40 mV or more depolarized, while at 10(-5) M, channels were open at all voltages tested (-40 to +60 mV). In intact patches, channels were seen at depolarized patch potentials of +50 mV or greater, indicating that the ionized calcium concentration in the macrophage is probably less than 10(-7) M.
在培养的人巨噬细胞的完整膜片和切除的膜片中记录到了单钙激活钾通道电流。在对称的145 mM K⁺中通道电导为240 pS，在外部K⁺为5 mM时电导为130 pS。在一些膜片中观察到较低电导的电流波动（为较大通道的40%），其反转电位与较高电导通道相同。离子替代实验表明该通道对钾有通透性，而对钠相对不通透。通道开放频率随去极化和细胞内钙浓度增加而增加。在细胞内钙浓度为10⁻⁷ M时，通道活性仅在去极化至 +40 mV或更高电位时才明显，而在10⁻⁵ M时，在所有测试电压（-40至 +60 mV）下通道均开放。在完整膜片中，在膜片去极化至 +50 mV或更高电位时可观察到通道，这表明巨噬细胞中的离子化钙浓度可能低于10⁻⁷ M。
