ENERGETIC SUPPORT OF POST-ISCHEMIC CARDIAC PERFORMANCE

为缺血后心脏功能提供能量支持

• 批准号: 2226640
• 负责人: ROBERT T MALLET
• 金额: $ 9.5万
• 依托单位: UNIVERSITY OF NORTH TEXAS HLTH SCI CTR
• 依托单位国家: 美国
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-08-01 至 1998-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2226640
• 关键词: beta adrenergic agent; bioenergetics; calcium transporting ATPase; cardiotonic agents; coronary occlusion /thrombosis; disease /disorder model; guinea pigs; heart contraction; heart function; heart pharmacology; isoproterenol; myocardial ischemia /hypoxia; phospholamban; phosphorylation; protein kinase; pyruvates; radioimmunoassay; radiotracer; sarcoplasmic reticulum

Contractile function is depressed for prolonged periods in reversibly injured, viable myocardium following relatively brief coronary occlusions. Although recognized as an important clinical problem, the pathophysiological mechanisms of this myocardial 'stunning' are controversial. We have developed and characterized an isolated working guinea-pig heart model of stunning. In these hearts, the energy-yielding substrate pyruvate produces marked, parallel enhancements of ventricular performance and myocytic energy level (cytosolic ATP phosphorylation potential and Gibbs free energy of ATP hydrolysis). The overall goal of this research is to delineate the subcellular mechanisms responsible for these energy-linked functional improvements. Myocardial function is controlled in large measure by the Ca2+ pumping activity of the sarcoplasmic reticulum Ca2+ ATPase. Our preliminary findings indicate that pyruvate-energization enhances sarcoplasmic reticulum Ca2+_ transport in non-ischemic heart. Project one will test the hypothesis that cytosolic energization stimulates Ca2+ uptake by sarcoplasmic reticulum in post-ischemic 'stunned' myocardium. Cytosolic energy level in 'stunned' guinea-pig hearts will be varied by altering substrate composition of perfusion media or by beta-adrenergic stimulation with isoproterenol, and Ca2+ uptake and Ca2+ ATPase activity will be quantitated in sarcoplasmic reticulum isolated from stop-frozen hearts. Project two will test the hypothesis that substrate-enhancement of sarcoplasmic reticular function stems from increased phospholamban phosphorylation, a well-characterized mechanism for beta-adrenergic stimulation of cardiac inotropism. To effect radiolabelling of cardiac phosphoproteins, intramyocytic high-energy phosphate pools will be labelled by perfusion with [32P]inorganic phosphate; during tracer-free washout, cardiac inotropism will be increased by pyruvate-energization or by beta-adrenergic stimulation with isoproterenol. Proteins in isolated sarcoplasmic reticulum will be separated by electrophoresis, and 32P incorporation detected and quantitated by autoradiography and scintillation counting. This investigation will delineate the bioenergetic mechanisms for the observed highly significant relationship between contractility and cytosolic energy level in normoxic and especially 'stunned' myocardium in the absence of adrenergic stimulation. Of special clinical interest, pyruvate energization may be effective in reversing postischemic impairment of sarcoplasmic reticulum Ca2+ transport. Since pyruvate, unlike catecholamines, increases cytosolic energy level, this investigation may indicate that pyruvate could be a valuable cardioprotective intervention in clinical situations of energy-depleted heart.

收缩功能可逆地长时间降低 相对短暂的冠状动脉后受伤，可行的心肌 闭塞。 尽管被认为是一个重要的临床问题 这种心肌“惊人”的病理生理机制是 有争议的。 我们已经开发并表征了一个孤立的工作 豚鼠心脏模型。 在这些心中，能量赋予能量 基质丙酮酸会产生标志性的，平行的心室增强 性能和心肌能水平（胞质ATP磷酸化 ATP水解的潜力和吉布斯自由能）。 总体目标 这项研究是为了描述负责的亚细胞机制 这些能量连接的功能改进。 心肌功能是 由Ca2+抽水活动在很大程度上控制 肌质网Ca2+ ATPase。 我们的初步发现表明 丙酮酸促进能增强肌质网Ca2+_ 非缺血性心脏的运输。 项目第一将检验假设 胞质能量刺激了肌质的Ca2+摄取 缺血后的“震惊”心肌的网状。 胞质能级 在“震惊”的豚鼠心中将通过更改底物来改变 灌注培养基或通过β-肾上腺素能刺激的组成 异丙肾上腺素，Ca2+摄取和Ca2+ ATPase活性将是 在从停止冻结的心脏中分离出来的肌质网中定量。 项目第二将检验以下假设 肌质性网状功能源于磷酸兰班的增加 磷酸化，一种β-肾上腺素能特征良好的机制 刺激心脏肌功能障碍。 实现心脏的放射性标记 磷酸蛋白，细胞内高能磷酸盐池将是 用[32p]无机磷酸盐灌注标记；在无示踪剂期间 冲洗，心脏肌功能抗体将通过丙酮酸增强增加 或通过异丙肾上腺素β-肾上腺素能刺激。 蛋白质中的蛋白质 分离的肌质网将通过电泳分离，并且 通过放射自显影检测并定量32p掺入 闪烁计数。 这项调查将描绘出的生物能机制 观察到收缩性和 胞质能水平在常氧中，尤其是“震惊”的心肌 在没有肾上腺素能刺激的情况下。 特别临床感兴趣， 丙酮酸能量可能有效地逆转缺血后 肌质网Ca2+转运的损害。 自丙酮酸以来 与儿茶酚胺不同，可以提高胞质能水平，这 调查可能表明丙酮酸可能是有价值的 在能量消耗的临床情况下进行心脏保护干预 心。