Park Won Sun, Han Jin, Kim Nari, Youm Jae Boum, Joo Hyun, Kim Hyung Kyu, Ko Jae-Hong, Earm Yung E
Mitochondrial Signaling Laboratory, Department of Physiology and Biophysics, College of Medicine, Biohealth Products Research Center, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Korea.
J Cardiovasc Pharmacol. 2005 Nov;46(5):681-9. doi: 10.1097/01.fjc.0000182846.08357.ed.
We studied inward rectifier K+ (Kir) channels in smooth muscle cells isolated from rabbit coronary arteries. In cells from small- (<100 microm, SCASMC) and medium-diameter (100 approximately 200 microm, MCASMC) coronary arteries, Kir currents were clearly identified (11.2 +/- 0.6 and 4.2 +/- 0.6 pA pF at -140 mV in SCASMC and MCASMC, respectively) that were inhibited by Ba(2+) (50 microm). By contrast, a very low Kir current density (1.6 +/- 0.4 pA pF) was detected in cells from large-diameter coronary arteries (>200 microm, LCASMC). The presence of Kir2.1 protein was confirmed in SCASMC in a Western blot assay. Endothelin-1 (ET-1) inhibited Kir currents in a dose-dependent manner. The inhibition of Kir currents by ET-1 was abolished by pretreatment with the protein kinase C (PKC) inhibitor staurosporine (100 nM) or GF 109203X (1 microm). The PKC activators phorbol 12,13-dibutyrate (PDBu) and 1-oleoyl-2-acetyl-sn-glycerol (OAG) reduced Kir currents. The ETA-receptor inhibitor BQ-123 prevented the ET-1-induced inhibition of Kir currents. The amplitudes of the ATP-dependent K+ (KATP), Ca(2+)-activated K+ (BKCa), and voltage-dependent K+ (KV) currents, and effects of ET-1 on these channels did not differ between SCASMC and LCASMC. From these results, we conclude that Kir channels are expressed at a higher density in SCASMC than in larger arteries and that the Kir channel activity is negatively regulated by the stimulation of ETA-receptors via the PKC pathway.
我们研究了从兔冠状动脉分离出的平滑肌细胞中的内向整流钾离子（Kir）通道。在来自小直径（<100微米，SCASMC）和中直径（100至200微米，MCASMC）冠状动脉的细胞中，明确鉴定出了Kir电流（在-140 mV时，SCASMC和MCASMC中的Kir电流分别为11.2±0.6和4.2±0.6 pA pF），这些电流可被50微摩尔的Ba(2+)抑制。相比之下，在大直径冠状动脉（>200微米，LCASMC）的细胞中检测到非常低的Kir电流密度（1.6±0.4 pA pF）。通过蛋白质印迹分析在SCASMC中证实了Kir2.1蛋白的存在。内皮素-1（ET-1）以剂量依赖性方式抑制Kir电流。蛋白激酶C（PKC）抑制剂星形孢菌素（100 nM）或GF 109203X（1微摩尔）预处理可消除ET-1对Kir电流的抑制作用。PKC激活剂佛波醇12,13-二丁酸酯（PDBu）和1-油酰基-2-乙酰基-sn-甘油（OAG）可降低Kir电流。ETA受体抑制剂BQ-123可阻止ET-1诱导的Kir电流抑制。ATP依赖性钾离子（KATP）、钙激活钾离子（BKCa）和电压依赖性钾离子（KV）电流的幅度以及ET-1对这些通道的影响在SCASMC和LCASMC之间没有差异。从这些结果中，我们得出结论，Kir通道在SCASMC中的表达密度高于较大动脉，并且Kir通道活性通过PKC途径被ETA受体的刺激负向调节。
