EXERCISE AND CORONARY ADENOSINE ACTIVATED K CURRENTS

运动和冠状动脉腺苷激活 K 电流

• 批准号: 6343574
• 负责人: DOUGLAS K BOWLES
• 金额: $ 9.35万
• 依托单位: UNIVERSITY OF MISSOURI-COLUMBIA
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-01-01 至 2002-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6343574
• 关键词: G protein; adenosine; adenylate cyclase; calcium ion; confocal scanning microscopy; exercise; fluorimetry; heart function; lasers; muscle relaxation; myocardium; potassium channel; potassium ion; protein kinase A; sarcolemma; statistics /biometry; vascular smooth muscle; vasodilatation; voltage /patch clamp

DESCRIPTION (Adapted from the applicant's abstract): Exercise training may provide cardioprotection through increased coronary sensitivity to adenosine (ADO), a cardioprotective, hyperpolarizing vasodilator. The mechanism of enhanced sensitivity to ADO following EX is unknown, but may involve increased K channel activation. The long-term objective of this project is to determine the effect of EX on ADO stimulation of K currents in coronary smooth muscle (CSM) from different coronary vascular regions. Preliminary studies provide novel evidence that the K channel responsible for ADO-activated K current in resistance arteries is a large-conductance, Ca-activated K channel (KCa). Therefore, this project will determine by what mechanism KCa channels are activated by ADO in sedentary animals and following EX, and the arterial size dependence (conduit vs. resistance) of this effect. The overall hypothesis is that ADO activates KCa channels due to an increase in subsarcolemmal Ca independent of changes in bulk myoplasmic Ca due to Ca "unloading" from the SR. Furthermore, in SED, this activation occurs in resistance, but not conduit coronary arteries. Second, EX produces and "upstream shift" in the response to ADO, such that conduit arteries exhibit ADO-activated K current similar to resistance arteries from SED. In intact arteries, this enhanced ADO-stimulated K current will account, in part, for the enhanced vasodilation/relaxation following EX. The specific aims are to determine: 1) the effect of ADO and ADO analogs on K current in CSM from resistance and conduit arteries in SED and EX, 2) the type of K channel responsible for ADO-activated K current, 3) the role of G proteins, adenylate cyclase, and PKA in the activation of K current by ADO, 4) the role and source of subsarcolemmal Ca in KCa activation by ADO and 5) the contribution of K channels to the decrease in Cam and vasorelaxation following EX. Methods: Resistance (100-250 micron ID) and conduit (over 1 mm ID) arteries will be obtained from miniature swine following 16 wk of EX and compared to SED. K current and intracellular Ca will be determined by simultaneous voltage-clamp and fura-2 microfluorometry or high speed laser scanning confocal microscopy. Functional data will be obtained from simultaneous Cam and tension/diameter measures in intact arteries. The significance of the proposed study would be to; 1) provide the first direct evidence for, and mechanism of, KCa channel activation by ADO in CSM cells, 2) expand current information regarding the functional heterogeneity in the coronary vasculature to the subcellular level, and 3) provide a mechanism for enhanced coronary vasodilation to ADO after EX.

描述（改编自申请人的摘要）：运动训练可以 通过增加冠状动脉对腺苷的敏感性提供心脏保护 (ADO)是一种心脏保护性的超极化血管扩张剂。 的机理 EX后对ADO的敏感性增强尚不清楚，但可能涉及 增加K通道激活。 该项目的长期目标是 确定EX对ADO刺激冠状动脉钾电流的影响， 平滑肌（CSM）从不同的冠状动脉血管区域。 初步 研究提供了新的证据，K通道负责 ADO激活的K电流在阻力动脉中是一个大电导， 钙激活钾通道（KCa）。 因此，本项目将通过 ADO在久坐动物中激活KCa通道的机制， EX之后，以及以下的动脉尺寸依赖性（导管与阻力）： 这种效果。 总体假设是，由于ADO激活KCa通道， 肌膜下钙的增加与体积的变化无关 肌浆钙由于钙“卸载”从SR。此外，在SED，这 激活发生在阻力，而不是导管冠状动脉。 第二、 EX在响应ADO时产生“上游移位”， 动脉表现出类似于阻力动脉的ADO激活K电流， SED。 在完整的动脉中，这种增强的ADO刺激的K电流将 部分原因是EX后血管舒张/舒张增强。 具体目的是确定：1）ADO和ADO类似物对 在SED和EX中，CSM中来自阻力动脉和管道动脉的K电流; 2） 型钾通道负责ADO激活的钾电流，3）G的作用 腺苷酸环化酶和PKA在ADO激活K电流中的作用， 4)肌膜下Ca在ADO激活KCa中作用及来源 K通道对降低Cam和血管舒张的贡献 继EX。 方法：电阻（100-250微米ID）和导管（超过1 将在16周的EX后从小型猪中获得2 mm ID）动脉 与之相比， K电流和细胞内Ca将通过 同时电压钳和Fura-2显微荧光测定法或高速激光 扫描共聚焦显微镜。 功能数据将从 在完整动脉中同时测量Cam和张力/直径。 的 该研究的意义在于：（1）提供第一个直接的 在CSM细胞中ADO激活KCa通道的证据和机制， 2)扩大目前的信息有关的功能异质性， 冠状动脉血管系统的亚细胞水平，和3）提供一种机制， 用于增强EX后ADO的冠状血管舒张。