Role of SKCa and IKCa in endothelium-dependent hyperpolarizations of the guinea-pig isolated carotid artery
Role of SKCa and IKCa in endothelium-dependent hyperpolarizations of the guinea-pig isolated carotid artery
复制标题
DOI：
10.1038/sj.bjp.0706003
复制
发表时间：
2005-02-01
影响因子：
7.3
通讯作者：
Félétou, M
中科院分区：
文献类型：
--
作者：
Gluais, P;Edwards, G;Félétou, M
1 本研究旨在确定豚鼠颈动脉中乙酰胆碱引起的内皮依赖性超极化是否涉及细胞色素 P450 代谢物，以及它们是否与两种不同的内皮 K-Ca 通道群 SKCa 和 IKCa 的激活有关。2 在豚鼠离体颈动脉的血管平滑肌细胞中记录了膜电位。所有实验均在 N(o)omegaL-硝基精氨酸 (100 μM) 和吲哚美辛 (5 μM) 存在下进行。3 在对照条件下 (Ca2+：2.5 mM)，乙酰胆碱（10 nM 至 10 μM）诱导血管平滑肌细胞的浓度和内皮依赖性超极化。两种结构不同的 SKCa 特异性阻断剂，apamin (0.5 μM) 或 UCL 1684 (10 μM)，对乙酰胆碱引起的超极化产生部分但显着的抑制作用，而 Charybdotoxin (0.1 μM) 和 TRAM-34 (10 μM)（一种非肽类 IKCa 特异性阻断剂）无效。相比之下，apamin 加 Charybdotoxin、apamin 加 TRAM-34 (10 muM) 或 U CL 1684 (10 muM) 加 TRAM-34 (10 muM) 的组合实际上消除了乙酰胆碱诱导的超极化。 4 在 apamin 和亚有效剂量的 TRAM-34 (5 muM) 组合存在的情况下，乙酰胆碱产生的残余超极化没有被抑制进一步通过添加环氧二十碳三烯酸拮抗剂 14,15-EEZE (10 muM) 或 BKCa 特异性阻断剂伊贝里奥毒素 (0.1 muM)。5 在 0.5 mM Ca2+ 存在下，对乙酰胆碱 (1 muM) 的超极化反应显着低于 2.5 mM Ca2+。 EDHF 介导的反应主要对 Charybdotoxin 或 TRAM-34 敏感，但对 apamin 具有抗性。 6 这项研究表明，细胞色素 P450 代谢物的产生以及随后 BKCa 的激活不太可能对豚鼠颈动脉中 EDHF 介导的反应做出贡献。此外，EDHF 介导的反应涉及内皮 IKCa 和 SKCa 通道的激活，任一通道的激活都能够产生真正的超极化。
1 This study was designed to determine whether the endothelium-dependent hyperpolarizations evoked by acetylcholine in guinea-pig carotid artery involve a cytochrome P450 metabolite and whether they are linked to the activation of two distinct populations of endothelial K-Ca channels, SKCa and IKCa.2 The membrane potential was recorded in the vascular smooth muscle cells of the guinea-pig isolated carotid artery. All the experiments were performed in the presence of N(o)omegaL-nitro arginine (100 muM) and indomethacin (5 muM).3 Under control conditions (Ca2+: 2.5 mM), acetylcholine (10 nM to 10 muM) induced a concentration- and endothelium-dependent hyperpolarization of the vascular smooth muscle cells. Two structurally different specific blockers of SKCa, apamin (0.5 muM) or UCL 1684 (10 muM), produced a partial but significant inhibition of the hyperpolarization evoked by acetylcholine whereas charybdotoxin (0.1 muM) and TRAM-34 (10 muM), a nonpeptidic and specific blocker of IKCa, were ineffective. In contrast, the combinations of apamin plus charybdotoxin, apamin plus TRAM-34 (10 muM) or U CL 1684 (10 muM) plus TRAM-34 (10 muM) virtually abolished the acetylcholine-induced hyperpolarization.4 In the presence of a combination of apamin and a subeffective dose of TRAM-34 (5 muM), the residual hyperpolarization produced by acetylcholine was not inhibited further by the addition of either an epoxyeicosatrienoic acid antagonist, 14,15-EEZE (10 muM) or the specific blocker of BKCa, iberiotoxin (0.1 muM).5 In presence of 0.5 mM Ca2+, the hyperpolarization in response to acetylcholine (1 muM) was significantly lower than in 2.5 mM Ca2+. The EDHF-mediated responses became predominantly sensitive to charybdotoxin or TRAM-34 but resistant to apamin.6 This investigation shows that the production of a cytochrome P450 metabolite, and the subsequent activation of BKCa, is unlikely to contribute to the EDHF-mediated responses in the guinea-pig carotid artery. Furthermore, the EDHF-mediated response involves the activation of both endothelial IKCa and SKCa channels, the activation of either one being able to produce a true hyperpolarization.