ENERGETIC SUPPORT OF POST-ISCHEMIC CARDIAC PERFORMANCE

收缩功能可逆性长时间受抑制 相对短暂的冠状动脉病变后受损、存活的心肌 闭塞。尽管被认为是一个重要的临床问题，但 这种心肌“顿抑”的病理生理机制是 有争议的。我们已经开发并描述了一种孤立的工作 豚鼠心脏模型的惊艳。在这些人的心中，产生能量的 丙酮酸底物可显著、平行地增强脑室 表现和肌细胞能量水平(胞浆ATP磷酸化 ATP水解势和吉布斯自由能)。的总目标是 这项研究是为了描绘负责的亚细胞机制 这些与能量相关的功能改进。心肌功能是 在很大程度上受细胞内钙泵活性的控制 肌浆网钙ATPase。我们的初步调查结果表明 丙酮酸充能增强肌浆网钙离子 在非缺血心脏中的转运。项目一将检验这一假设 胞浆能化刺激肌浆钙摄取 缺血后“顿抑”心肌中的网状结构。胞质能级 受惊的豚鼠心脏将通过改变底物而发生变化 灌注液的成分或通过β-肾上腺素能刺激 异丙肾上腺素、钙摄取和钙ATPase活性 在从停止冷冻的心脏分离的肌浆网中定量。 项目二将测试底物增强的假说 肌浆网功能源于磷蛋白的增加 磷酸化--β-肾上腺素能的一种很好的机制 心脏变力作用的刺激。以实现心脏的放射性标记 磷蛋白、肌细胞内高能磷酸盐池将 用[32P]无机磷酸盐灌流标记；在无示踪剂期间 洗涤，丙酮酸供能会增加心脏的变力作用 或通过异丙肾上腺素的β-肾上腺素能刺激。中的蛋白质 分离的肌浆网将通过电泳法分离，并 放射自显影检测和定量~(32)P掺入 闪烁计数。 这项研究将勾勒出生物能量机制 观察到的收缩性和 常氧心肌和特别是“顿抑”心肌的胞浆能量水平 在没有肾上腺素能刺激的情况下。有特殊的临床价值， 丙酮酸充能可能有效逆转脑缺血后 肌浆网钙转运障碍。因为丙酮酸， 与儿茶酚胺不同的是，它增加了细胞内的能量水平，这 调查可能表明，丙酮酸可能是一种有价值的 能量耗竭临床情况下的心脏保护干预 心。

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.