Sunose H, Ikeda K, Suzuki M, Takasaka T
Department of Otolaryngology, Tohoku University School of Medicine, Sendai, Japan.
Hear Res. 1994 Oct;80(1):86-92. doi: 10.1016/0378-5955(94)90012-4.
Inward rectifying K channel activity was observed in the luminal membrane of the marginal cell by use of the patch clamp technique. When pipette solution contained 150 mM KCl, the current reversed at 10.2 +/- 8.8 mV (N = 27). The channel current showed multiple subconductance levels and depolarization activated the channel very slowly (order of seconds). Current-voltage relationships in cell-attached mode showed inward rectification. The calculated slope conductance of inward and outward currents were 18 +/- 7 pS and 5.4 +/- 2.0 pS (N = 27), respectively. When pipette solution contained 75 mM NaCl and 75 mM KCl, the current reversed -7.0 +/- 7.6 mV (N = 6). When pipette solution contained NaCl or Na gluconate, the channel currents were outwardly directed within a range of -60 to 60 mV. These results suggested that the channel is selective to K+. The channel showed immediate run down after excision, and this rundown was not prevented by elimination of cytoplasmic Ca2+. The channel activity was not affected by an increase of intracellular cAMP and cGMP, an application of cytoplasmic catalytic subunit of PKA with ATP. Taking its density into consideration, the channel seems to contribute considerably to the K+ conductance of the luminal membrane of the marginal cell.
运用膜片钳技术在边缘细胞的管腔膜上观察到内向整流钾通道活性。当移液管溶液含有150 mM KCl时，电流在10.2±8.8 mV处反转（N = 27）。通道电流显示出多个亚电导水平，去极化激活通道非常缓慢（数秒级）。细胞贴附模式下的电流-电压关系显示出内向整流。内向和外向电流的计算斜率电导分别为18±7 pS和5.4±2.0 pS（N = 27）。当移液管溶液含有75 mM NaCl和75 mM KCl时，电流在-7.0±7.6 mV处反转（N = 6）。当移液管溶液含有NaCl或葡萄糖酸钠时，通道电流在-60至60 mV范围内向外。这些结果表明该通道对K +具有选择性。该通道在切除后立即出现电流衰减，并且消除细胞质Ca2 +并不能阻止这种衰减。通道活性不受细胞内cAMP和cGMP增加、应用带有ATP的PKA细胞质催化亚基的影响。考虑到其密度，该通道似乎对边缘细胞管腔膜的K +电导有很大贡献。
