Involvement of voltage‐dependent potassium channels in the EDHF‐mediated relaxation of rat hepatic artery
Involvement of voltage‐dependent potassium channels in the EDHF‐mediated relaxation of rat hepatic artery
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电压依赖性钾通道参与 EDHF 介导的大鼠肝动脉舒张
DOI：
10.1038/sj.bjp.0701108
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发表时间：
1997
影响因子：
7.3
通讯作者：
E. Högestätt
中科院分区：
文献类型：
--
作者：
P. Zygmunt;G. Edwards;A. Weston;B. Larsson;E. Högestätt
在大鼠肝动脉上，内皮源性超极化因子(EDHF)介导的乙酰胆碱所致的松弛可分别被阿帕明和查氏毒素、小(SKCa)和大(BKCa)电导钙敏感钾(K)通道的阻断剂所阻断，但不能单独被两种毒素所阻断。在这种组合中，选择性的BKCa抑制剂iberiooxin不能取代轮虫毒素。由于延迟整流钾通道(KV)是轮藻毒素的另一个靶点，我们探讨了KV可能参与EDHF介导的这条动脉的松弛。激动剂-2(0.3μM)、刺激性毒素(0.3μM)、树突状毒素(0.3μM)、多非利特(1μM)和替卡兰(10ωM)分别与阿帕明(0.3μM)联合应用，对N-硝基-L-精氨酸(0.3 mM)和吲哚美辛(10 MM)分别抑制一氧化氮合酶(NO)合成酶和环氧合酶抑制剂(n=2-3)所引起的内源性胆碱兴奋效应无明显影响。KV抑制剂麦草毒素(0.3μM)也无作用(n=5)，但麦草毒素与阿帕明合用对该反应有轻微的抑制作用(pEC_(50)和Emax分别为7.5±0.0和95±1%，麦草毒素加阿帕明存在时分别为7.0±0.1和81±6%；n=6；P<；0.05)。Ciclazindol(10μM)可使乙酰胆碱-量效曲线右移12倍(n=6；P<；0.05)，部分抑制EDH介导的舒缩作用，与阿帕明(0.3μM；n=6)合用可完全阻断此效应。这种联合作用不能抑制内皮源性NO(n=5)介导的乙酰胆碱所致的舒缩反应。在新鲜分离的大鼠肝动脉单个平滑肌细胞上观察到4-氨基吡啶敏感的延迟整流电流(IK(V))。所有细胞均未出现快速激活和失活的A型电流。白纹藻毒素(0.3μM；n=3)和环吲哚(10μM；n=5)单独或与阿帕明(0.3μM；n=4-5)联合应用对IK(V)均无影响。10倍浓度的西拉津多(0.1mM，n=4)可显著抑制IK(V)，而阿帕明(0.3μM；n=2)对此作用无明显影响。利用从大鼠大脑皮质制备的膜，[125I]-白纹藻毒素结合符合单一位置的相互作用，Kd值约为25 pm。[125I]-角藻毒素结合不受伊贝毒(0.1μM，n=6)的影响，但被apamin以浓度依赖的方式增加(Emax 43±10%，P<；0.05和pEC507.1±0.2；n=7~8)。Agitoxin-2(10 NM)使[125I]-查氏毒素结合位移91±3%(n=6)，并阻断阿帕明(1μM；n=6)的作用。结论：EDHF介导的大鼠肝动脉松弛不是通过开放KV或BKCa介导的。相反，EDHF的目标K通道似乎在结构上与KV和BKCa有关。讨论了SKCa亚型可能成为EDHF的靶标的可能性。
In the rat hepatic artery, the acetylcholine‐induced relaxation mediated by endothelium‐derived hyperpolarizing factor (EDHF) is abolished by a combination of apamin and charybdotoxin, inhibitors of small (SKCa) and large (BKCa) conductance calcium‐sensitive potassium (K)‐channels, respectively, but not by each toxin alone. The selective BKCa inhibitor iberiotoxin cannot replace charybdotoxin in this combination. Since delayed rectifier K‐channels (KV) represent another target for charybdotoxin, we explored the possible involvement of KV in EDHF‐mediated relaxation in this artery. The KV inhibitors, agitoxin‐2 (0.3 μM), kaliotoxin (0.3 μM), β‐dendrotoxin (0.3 μM), dofetilide (1 μM) and terikalant (10 μM), each in combination with apamin (0.3 μM) had no effect on the EDHF‐mediated relaxation induced by acetylcholine in the presence of Nω‐nitro‐L‐arginine (0.3 mM) and indomethacin (10 μM), inhibitors of nitric oxide (NO) synthase and cyclo‐oxygenase, respectively (n=2–3). Although the KV inhibitor margatoxin (0.3 μM) was also without effect (n=5), the combination of margatoxin and apamin produced a small inhibition of the response (pEC50 and Emax values were 7.5±0.0 and 95±1% in the absence and 7.0±0.1 and 81±6% in the presence of margatoxin plus apamin, respectively; n=6; P<0.05). Ciclazindol (10 μM) partially inhibited the EDHF‐mediated relaxation by shifting the acetylcholine‐concentration‐response curve 12 fold to the right (n=6; P<0.05) and abolished the response when combined with apamin (0.3 μM; n=6). This combination did not inhibit acetylcholine‐induced relaxations mediated by endothelium‐derived NO (n=5). A 4‐aminopyridine‐sensitive delayed rectifier current (IK(V)) was identified in freshly‐isolated single smooth muscle cells from rat hepatic artery. None of the cells displayed a rapidly‐activating and ‐inactivating A‐type current. Neither charybdotoxin (0.3 μM; n=3) nor ciclazindol (10 μM; n=5), alone or in combination with apamin (0.3 μM; n=4–5), had an effect on IK(V). A tenfold higher concentration of ciclazindol (0.1 mM, n=4) markedly inhibited IK(V), but this effect was not increased in the additional presence of apamin (0.3 μM; n=2). By use of membranes prepared from rat brain cortex, [125I]‐charybdotoxin binding was consistent with an interaction at a single site with a KD of approximately 25 pM. [125I]‐charybdotoxin binding was unaffected by iberiotoxin (0.1 μM, n=6), but was increased by apamin in a concentration‐dependent manner (Emax 43±10%, P<0.05 and pEC50 7.1±0.2; n=7–8). Agitoxin‐2 (10 nM) displaced [125I]‐charybdotoxin binding by 91±3% (n=6) and prevented the effect of apamin (1 μM; n=6). It is concluded that the EDHF‐mediated relaxation in the rat hepatic artery is not mediated by the opening of either KV or BKCa. Instead, the target K‐channels for EDHF seem to be structurally related to both KV and BKCa. The possibility that a subtype of SKCa may be the target for EDHF is discussed.
影响因子：
2.9
作者：
GARCIA, ML;GARCIACALVO, M;MACKINNON, R
通讯作者：
MACKINNON, R
DOI：
--
发表时间：
1993
期刊：
The Journal of pharmacology and experimental therapeutics
影响因子：
--
作者：
Cowan,CL;Palacino,JJ;Najibi,S;Cohen,RA
通讯作者：
Cohen,RA
乙醇调节[125I]钙调蛋白与大鼠脑突触质膜的结合。
DOI：
--
发表时间：
1994
期刊：
The Journal of pharmacology and experimental therapeutics
影响因子：
--
作者：
Sze,PY;Iqbal,Z
通讯作者：
Iqbal,Z