Selective blockade of endothelial Ca2+-activated small- and intermediate-conductance K+-channels suppresses EDHF-mediatied vasodilation
Selective blockade of endothelial Ca2+-activated small- and intermediate-conductance K+-channels suppresses EDHF-mediatied vasodilation
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DOI：
10.1038/sj.bjp.0705075
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发表时间：
2003-02-01
影响因子：
7.3
通讯作者：
Köhler, R
中科院分区：
文献类型：
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作者：
Eichler, I;Wibawa, J;Köhler, R
1钙激活钾通道（K-Ca）的激活在内皮源性超极化因子（EDHF）介导的血管舒张中起关键作用。然而，由于常用的K-Ca通道阻断剂的低选择性，仍然难以确定哪种内皮K-Ca亚型介导超极化，从而启动EDHF介导的血管舒张。（2-氯苯基）二苯基甲基]-1H-吡唑（TRAM-34）和2-（2-氯苯基）-2，2-二苯乙腈（TRAM-39）作为高选择性IK 1抑制剂，我们研究了中电导K-Ca（rIK 1）在内皮超极化和EDHF介导的血管舒张中的作用。在大鼠颈动脉（CA）单个内皮细胞中原位显示电导K-Ca（rSK 3）。rIK 1-电流被TRAM-34或TRAM-39阻断，而rSK 3被apamin阻断。在电流钳实验中，响应于乙酰胆碱的内皮超极化被apamin和TRAM-34.4的组合废除在苯肾上腺素预收缩的CA，乙酰胆碱诱导的NO和前列环素非依赖性血管舒张几乎完全被ChTX，CLT，TRAM-34，或TRAM-39与SK 3阻断剂apamin的组合阻断。Apamin、TRAM-34和CLT单独或磺胺苯唑（细胞色素P450亚型2C 9的阻断剂）在阻断EDHF反应方面无效。5在不阻断NO和前列环素合成的实验中，SK 3和IK 1的联合阻断降低了内皮依赖性血管舒张。6总之，选择性IK 1抑制剂与SK 3阻断剂apamin一起使用揭示了K-Ca，rIK 1和rSK 3在介导内皮超极化和EDHF信号产生中至关重要，而细胞色素P450途径似乎在大鼠CA中起次要作用或不起作用。
1 Activation of Ca2+-activated K+-channels (K-Ca) has been suggested to play a key role in endothelium-derived hyperpolarizing factor (EDHF)-mediated vasodilation. However, due to the low selectivity of commonly used K-Ca-channel blockers it is still elusive which endothelial K-Ca-subtypes mediate hyperpolarization and thus initiate EDHF-mediated vasodilation.2 Using the non-cytochrome P450 blocking clotrimazole-derivatives, 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) and 2-(2-chlorophenyl)-2,2-diphenylacetonitrile (TRAM-39) as highly selective IK1-inhibitors, we investigated the role of the intermediate-conductance K-Ca (rIK1) in endothelial hyperpolarization and EDHF-mediated vasodilation.3 Expression and function of rIK1 and small-conductance K-Ca (rSK3) were demonstrated in situ in single endothelial cells of rat carotid arteries (CA). rIK1-currents were blocked by TRAM-34 or TRAM-39, while rSK3 was blocked by apamin. In current-clamp experiments, endothelial hyperpolarization in response to acetylcholine was abolished by the combination of apamin and TRAM-34.4 In phenylephrine-preconstricted CA, acetylcholine-induced NO and prostacyclin-independent vasodilation was almost completely blocked by ChTX, CLT, TRAM-34, or TRAM-39 in combination with the SK3-blocker apamin. Apamin, TRAM-34, and CLT alone or sulphaphenzole, a blocker of the cytochrome P450 isoform 2C9, were ineffective in blocking the EDHF-response.5 In experiments without blocking NO and prostacyclin synthesis, the combined blockade of SK3 and IK1 reduced endothelium-dependent vasodilation.6 In conclusion, the use of selective IK1-inhibitors together with the SK3-blocker apamin revealed that activation of both K-Ca, rIK1 and rSK3 is crucial in mediating endothelial hyperpolarization and generation of the EDHF-signal while the cytochrome P450 pathway seems to play a minor or no role in rat CA.