Electropharmacological study of receptor-mediated regulation of cardiac Na^+-activated K^+ channels

受体介导的心脏Na^激活K^通道调节的电药理学研究

• 批准号: 08670102
• 负责人: NAKAYA Haruaki
• 金额: $ 1.41万
• 依托单位: Chiba University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08670102/
• 关键词: Na^+-activated K^+ channel; endothelin-1; beta_1-adrenoceptor; ET_A receptor; protein kinase A; 心筋細胞; Na^+活性化 K^+チャネル; ET_A; エンドセリン; β受容体

The Na<@D1+@>D1-activated K<@D1+@>D1 (K<@D2Na@>D2) channel has a large unitary conductance and is activated by an increase in the Na<@D1+@>D1 concentration at the inner side of the sarcolemma. It has been postulated that the K<@D2Na@>D2 channels may be activated not only in pathological conditions such as myocardial ischemia and digitalis toxicity but also in physiological conditions. However, it has not been determined whether cardiac K<@D2Na@>D2 channels are regulated by some receptor mechanisms. In this study I examined the effects of beta-adrenoceptor and endothelin (ET) receptor stimulation on the K<@D2Na@>D2 current in guinea pig ventricular cells by using patch clamp techniques. The K<@D2Na@>D2 current was activated by intracellular loading of 50 mM Na<@D1+@>D1 and extracellular application of 10 muM ouabain. Endothelin-1 (ET-1) at a concentration of 10 nM inhibited the K<@D2Na@>D2 current by 21(]SY.+-。[)4% (n=5), which was blocked by the selective ET<@D2A@>D2 receptor antagonis … More t BQ-485 (100 nM).Endothelin-3 (ET-3,30 nM) failed to inhibit the K<@D2Na@>D2 current. Neither protein kinase C inhibitor (staurosporine, calphostin C) nor intracellular loading of inositol 1,4,5-trisphosphate (IP<@D23@>D2) affected the K<@D2Na@>D2 current inhibition by ET-1. Isoproterenol (ISO,1-1000 nM) also inhibited the K<@D2Na@>D2 current in a concentration-dependent manner. The ISO (100 nM) -induced decrease of the K<@D2Na@>D2 current was abolished by 10 muM atenolol but not by 100 nM ICI 118,551, indicating the involvement of beta<@D21@>D2-adrenoceptors. Forskolin (10 muM) also inhibited the K<@D2Na@>D2 current and the ISO-induced K<@D2Na@>D2 current inhibition was attenuated by the intracellular loading of protein kinase inhibitor peptide. Therefore, cAMP-protein kinase A pathway plays an important role in the beta<@D21@>D2-adrenoceptor-mediated inhibition of the K<@D2Na@>D2 current. Thus, both ET<@D2A@>D2 receptor an beta<@D21@>D2-adrenoceptor stimulation inhibit the cardiac K<@D2Na@>D2 current and modulate the action potential repolarization in pathological as well as physiological conditions. Less

Na<@D1+@>D1 激活的 K<@D1+@>D1 (K<@D2Na@>D2) 通道具有较大的单位电导，并且通过增加 Na<@D1+@>D1 浓度来激活据推测，K<@D2Na@>D2通道不仅在心肌缺血和洋地黄毒性等病理条件下可能被激活。然而，尚未确定心脏 K<@D2Na@>D2 通道是否受到某些受体机制的调节。在这项研究中，我检查了 β-肾上腺素受体和内皮素 (ET) 受体刺激对 K<@D2Na@>D2 通道的影响。使用膜片钳技术观察豚鼠心室细胞中的@D2Na@>D2电流 K<@D2Na@>D2电流通过细胞内负载50mM Na<@D1+@>D1和D1来激活。细胞外施用浓度为 10 nM 的 10 muM 哇巴因-1 (ET-1) 可抑制 K<@D2Na@>D2 电流 21(]SY.+-.[)4% (n=5)，它被选择性 ET<@D2A@>D2 受体拮抗剂阻断……更多 t BQ-485 (100 nM)。Endothelin-3 (ET-3,30 nM) 未能抑制 K<@D2Na@>D2 电流。蛋白激酶 C 抑制剂（十字孢菌素、calphostin C）和肌醇 1,4,5-三磷酸 (IP<@D23@) 的细胞内负载均无效。 >D2) 影响了 ET-1 的 K<@D2Na@>D2 电流抑制，异丙肾上腺素 (ISO,1-1000 nM) 也抑制了 K<@D2Na@>D2 电流。 K D2Na D2 电流以浓度依赖性方式被10 μM 阿替洛尔消除，但不能被100 nM ICI 118,551 消除。 β<@D21@>D2-肾上腺素受体的参与也抑制了这种作用。 K<@D2Na@>D2电流和ISO诱导的K<@D2Na@>D2电流抑制通过细胞内加载蛋白激酶抑制剂肽而减弱。因此，cAMP-蛋白激酶A途径在β<<<<<。 D21D2-肾上腺素受体介导的KD2NaD2电流的抑制因此，ETD2AD2受体和KD2NaD2电流均被抑制。 beta<@D21@>D2-肾上腺素受体刺激抑制心脏 K<@D2Na@>D2 电流并在病理和生理条件下调节动作电位复极化。