ACTIONS OF ADENOSINE IN NORMAL AND ISCHEMIC MYOCARDIUM

拟议研究的广泛和长期目标是进一步促进我们的 了解的病理生理学的机制， 心肌缺血-再灌注损伤和开发治疗方案 来治疗缺血性心脏 拟议的实验旨在 确定可逆性心肌缺血性损伤（称为 心肌顿抑）对兴奋-收缩偶联的影响，并确定 嘌呤核苷腺苷发挥其良好作用的机制- 对缺血后心室功能有公认的有益作用。 改变 顿抑心肌中的兴奋-收缩偶联被认为是由于 心肌能量学改变、收缩蛋白功能障碍，和/或 由于瞬时钙离子释放导致细胞内钙处理改变 超载。 心肌顿抑在临床上已被证明在病人 冠状动脉搭桥术和急性心肌梗死后溶栓治疗 心肌梗死 因此，所提出的实验在临床上是可行的。 对缺血性心脏病患者具有相关性和潜在治疗相关性 心脏病 心肌顿抑的影响及其衰减 腺苷治疗将在体内猪区域 心肌缺血模型和分离自正常和顿抑的心肌细胞 心肌 建议研究的具体目标是：（1） 确定体内心肌顿抑和瞬时钙离子浓度的影响 心肌能量学与基础和 刺激心肌收缩力。 预处理的影响， 腺苷或腺苷A1受体激动剂和拮抗剂， 心肌磷酸化潜力和正性肌力储备将是 评估。 (2)为了确定腺苷诱导的细胞凋亡的减弱 心肌顿抑与肌原纤维的正常化有关， 收缩性能 张力-pCa关系的评估， 最大缩短速度（Vmax）将在皮肤 制备分离自在体顿抑和正常猪心肌。 将对体内给药后的皮肤制剂进行研究。 用腺苷或腺苷A1受体激动剂预处理， 对手。 腺苷作用的具体机制， 肌丝将通过评估磷酸化状态来研究， 粗（c-蛋白，肌球蛋白LC 2）和细（TnT，TnT，Tm）丝蛋白 在不同的实验条件下。 (3)以确定是否 心肌顿抑与心肌细胞内Ca2+改变有关 体内平衡 基础和刺激的Ca2+电流和细胞内游离Ca2 + (Ca2+）i将在分离自正常和休克猪的肌细胞中测定 心肌 我们在这里的主要兴趣是阐明 腺苷处理对正常和顿抑心肌中Ca 2+稳态的影响。

The broad, long-term objectives of the proposed research are to further our understanding of the mechanisms underlying the pathophysiology of myocardial ischemia-reperfusion injury and to develop therapeutic regimens to treat the ischemic heart. The proposed experiments are designed to determine the effects of reversible myocardial ischemic injury (termed myocardial stunning) on excitation-contraction coupling, and to determine the mechanism by which the purine nucleoside adenosine exerts its well- recognized beneficial effect on postischemic ventricular function. Altered excitation-contraction coupling in stunned myocardium is thought to be due to altered myocardial energetics, contractile protein dysfunction, and/or altered intracellular calcium handling as a result of transient calcium overload. Myocardial stunning has been documented clinically in patients following coronary artery bypass surgery and thrombolysis after acute myocardial infarction. The proposed experiments thus are clinically relevant and of potential therapeutic relevance for humans with ischemic heart disease. The effects of myocardial stunning and its attenuation with adenosine treatment will be addressed in an in vivo porcine regional myocardial ischemia model and in myocytes isolated from normal and stunned myocardium. The specific aims of the proposed research are; (1) To determine the effects of in vivo myocardial stunning and transient calcium overload on the relationship between myocardial energetics and basal and stimulated myocardial contractility. The effects of pretreatment with adenosine or with adenosine A1 receptor agonists and antagonists on myocardial phosphorylation potential and inotropic reserve will be assessed. (2) To determine whether adenosine-induced attenuation of myocardial stunning is associated with a normalization of myofibrillar contractile properties. Assessments of tension-pCa relationships and maximum velocity of shortening (Vmax) will be determined in skinned preparations isolated from in vivo stunned and normal porcine myocardium. Studies will be performed on skinned preparations after in vivo pretreatment with adenosine or with adenosine A1 receptor agonists or antagonists. Specific mechanisms of adenosine action at the level of the myofilaments will be investigated by assessing phosphorylation states of thick (c-proteins, myosin LC2) and thin (TnT, TnT, Tm) filament proteins under various experimental conditions. (3) To determine whether myocardial stunning is associated with altered myocyte intracellular Ca2+ homeostasis. Basal and stimulated Ca2+ current and free intracellular (Ca2+)i will be determined in myocytes isolated from normal and stunned pig myocardium. Our main interest here is to elucidate the effects of adenosine treatment on Ca2+ homeostasis in normal and stunned myocardium.