Park M K, Lee S H, Lee S J, Ho W K, Earm Y E
Department of Physiology and Biophysics, College of Medicine, Seoul National University, Korea.
Pflugers Arch. 1995 Jul;430(3):308-14. doi: 10.1007/BF00373904.
We investigated the electrical responses of Ca-activated K (KCa) currents induced by hypoxia and reduction or oxidation of the channel protein in pulmonary (PASMC) and ear (EASMC) arterial smooth muscle cells using the patch-clamp technique. In cell-attached patches, in the presence of a high K solution (containing 0.316 microM Ca2+), the activity of KCa channels from PASMC was decreased (by 49 +/- 7% compared to control, pipette potential = -70 mV) by changing to a hypoxic solution (1 mM Na2S2O4, aeration with 100% N2 gas). EASMC channels did not respond to hypoxia. In order to investigate the possible mechanisms involved, using inside-out patches bathed symmetrically in 150 mM KCl, we applied redox couples to the intracellular side. Reducing agents, such as dithiothreitol (DDT, 5 mM), reduced glutathione, (GSH, 5 mM), and nicotinamide adenine dinucleotide reduced (NADH, 2 mM) decreased PASMC, but not EASMC, KCa channel activity. However, oxidizing agents such as 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB, 1 mM), oxidized glutathione (GSSG, 5 mM) and NAD (2 mM) increased KCa channel activity in both PASMC and EASMC. The increased activity due to oxidizing agents was restored by applying reducing agents. From these results, we could suggest that the basal redox state of the EASMC KCa channel is more reduced than that of the PASMC channel, since the response of KCa channels of the EASMC to intracellular reducing agents differs from that of the PASMC. This difference may be related to the different responses of PASMC and EASMC KCa channels to hypoxia.
我们使用膜片钳技术研究了缺氧以及通道蛋白还原或氧化对肺（PASMC）和耳（EASMC）动脉平滑肌细胞中钙激活钾（KCa）电流的电反应。在细胞贴附式膜片中，在高钾溶液（含0.316 microM Ca2+）存在的情况下，通过更换为缺氧溶液（1 mM Na2S2O4，用100%氮气曝气），PASMC的KCa通道活性降低（与对照相比降低49±7%，移液管电位 = -70 mV）。EASMC通道对缺氧无反应。为了研究其中可能涉及的机制，我们使用对称浸泡在150 mM KCl中的内向外膜片，将氧化还原对应用于细胞内侧。还原剂，如二硫苏糖醇（DDT，5 mM）、还原型谷胱甘肽（GSH，5 mM）和还原型烟酰胺腺嘌呤二核苷酸（NADH，2 mM）可降低PASMC而非EASMC的KCa通道活性。然而，氧化剂如5,5'-二硫代双（2-硝基苯甲酸）（DTNB，1 mM）、氧化型谷胱甘肽（GSSG，5 mM）和NAD（2 mM）可增加PASMC和EASMC的KCa通道活性。由于氧化剂导致的活性增加可通过应用还原剂恢复。从这些结果我们可以推测，EASMC KCa通道的基础氧化还原状态比PASMC通道的更还原，因为EASMC的KCa通道对细胞内还原剂的反应与PASMC不同。这种差异可能与PASMC和EASMC的KCa通道对缺氧的不同反应有关。
