EXERCISE AND CORONARY ADENOSINE ACTIVATED K CURRENTS

描述(改编自申请者的摘要)：运动训练可 通过增加冠状动脉对腺苷的敏感性来提供心脏保护 (ADO)，一种保护心脏的超极化血管扩张剂。它的作用机制 EX后对ADO的敏感性增强尚不清楚，但可能涉及 K通道激活增加。这个项目的长期目标是 EX对ADO刺激冠脉钾电流的影响 来自不同冠状动脉血管区域的平滑肌(CSM)。初步 研究提供了新的证据表明K通道负责 阻力动脉腺苷激活的钾电流是一种大电导， 钙激活的钾通道(Kca)。因此，这个项目将决定于 ADO激活KCA通道的机制是什么？ 以及动脉大小的依赖关系(管道与阻力)。 这种效果。总体假设是ADO激活KCA通道 肌膜下钙的增加不依赖于体积的变化 肌浆内钙从肌浆网“卸载”所致。此外，在SED中，这一点 激活发生在阻力冠状动脉，但不是管道冠状动脉。第二, EX在响应ADO时产生并“上游转移”，从而使管道 动脉呈现ADO激活的K电流，与阻力动脉相似 塞德。在完整的动脉中，这种增强的ADO刺激的K电流将 部分原因是运动后血管扩张/松弛增强。 具体目的是确定：1)ADO和ADO类似物对 SED和EX的阻力动脉和导管动脉在CSM上的钾电流，2) 负责ADO激活的钾电流的钾通道类型，3)G 蛋白质、腺苷环化酶和PKA在ADO激活钾电流中的作用 4)肌膜下钙在ADO激活KCA中的作用及来源 钾通道在钙调素和血管舒张性降低中的作用 在前一次之后。方法：电阻(100-250微米内径)和导管(大于1 Mm ID)动脉将在16周前从小型猪身上获得 并与SED进行了比较。钾电流和细胞内钙将由下列因素决定 同步电压钳和Fura-2微量荧光测定法或高速激光 扫描共聚焦显微镜。功能数据将从以下位置获得 在完整的动脉中同时测量CaM和张力/直径。这个 拟议研究的意义将是：1)提供第一个直接 ADO激活CSM细胞Kca通道的证据和机制， 2)扩展有关功能异构性的当前信息 冠脉血管形成到亚细胞水平，以及3)提供一种机制 用于增强冠状动脉血管扩张至ADO。

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.