Exercise Training and Myocardial K-ATP Channel Function

描述（由申请人提供）：众所周知，耐力运动训练（Tr）可以增强心脏对缺血再灌注损伤的抵抗力。迄今为止，这些适应的细胞基础尚未被清楚地确定。在心脏中，atp敏感的K通道存在于肌膜（sI-KATP）和线粒体（mito-KATP）上，两者都与保护心脏免受缺血性损伤有关。我们最近发现，Tr在单个大鼠心室心肌细胞中引起缺氧诱导的、格列苯脲敏感的外向K电流（IK，ATP）的显著降低。在Specific Aim 1中，我们将使用电生理（全细胞和切除的贴片）和免疫印迹技术来确定这一发现的细胞基础。我们将研究训练对(1)sI-KATP对ATP和ADP抑制的敏感性，(2)sI-KATP通道亚基（Kit6.2和SUR2A）的蛋白表达，以及(3)缺血应激时线粒体ATP生成的影响。我们还发现，在冠状动脉闭塞和再灌注引起的严重区域性缺血后，Tr在离体灌注心脏中产生了梗死区保留和增强的机械功能。我们还观察到明显的tr诱导充血，这在整个缺血再灌注方案中都很明显。在Specific Aim 2中，我们将使用选择性的sl-和mitto -KATP通道的KATP拮抗剂来确定这些特定通道在tr诱导的梗死保护和机械功能保护中的作用。吲哚美辛和L-NAME将在研究中用于确定缺血再灌注后充血的细胞基础，以及tr诱导的充血在多大程度上有助于心肌梗死的保全和心脏机械功能的保存。Aim 2的实验包括左室功能、代谢物、生化和冠状动脉血流的综合测量。

DESCRIPTION (provided by applicant): It is well known that endurance exercise training (Tr) renders the heart more resistant to ischemia and reperfusion injury. To date, the cellular basis for these adaptations has not been clearly identified. In the heart, ATP-sensitive K channels exist on the sarcolemma (sI-KATP) and in mitochondria (mito-KATP) and both have been implicated in protecting the heart against ischemic injury. We recently found that Tr elicits a marked reduction in the magnitude of an anoxia-inducible, glibenclamide-sensitive outward K current (IK,ATP) in single rat ventricular cardiocytes. In Specific Aim 1, we will use electrophysiological (whole cell and excised patch) and immunoblotting techniques to determine the cellular basis for this finding. We will examine the effect of training on (1) the sensitivity of sI-KATP to inhibition by ATP and ADP, (2) the protein expression of sI-KATP channel subunits (Kit6.2 and SUR2A), and (3) mitochondrial ATP production in the face of ischemic stress. We also found that following severe zonal ischemia elicited by coronary artery occlusion and then reperfusion, Tr produced infarct sparing and augmented mechanical function in isolated perfused hearts. We also observed a marked Tr-induced hyperemia that was apparent throughout the ischemia reperfusion protocol. In Specific Aim 2, we will use KATP antagonists that are selective for sl- and mito-KATP channels to identify the involvement of these specific channels in Tr-induced infarct sparing and preservation of mechanical function. Indomethacin and L-NAME will be used in studies to determine the cellular basis for the hyperemia that was exhibited during post-ischemic reperfusion, and the extent to which the Tr-induced hyperemia contributed to infarct sparing and the preservation of mechanical function in the heart. The experiments in Aim 2 include a comprehensive battery of LV function, metabolite, biochemical, and coronary flow measurements. Exercise training is known to be effective in the prevention and treatment of a wide variety of cardiopathologic conditions. Elucidation of the cellular changes that underlie these positive adaptations may be of particular importance in the design, development, and implementation of molecular and pharmacological heart disease treatment and prevention strategies. This is particularly significant in view of the fact that heart disease claims more North American lives than any other disease.