ACTIONS OF ADENOSINE IN NORMAL AND ISCHEMIC MYOCARDIUM

拟议研究的广泛和长期目标是促进我们的 对其病理生理学基础的认识 心肌缺血再灌注损伤及其治疗方案的研究进展 来治疗缺血性心脏。拟议中的实验旨在 确定可逆性心肌缺血损伤的影响(称为 心肌顿抑)对兴奋-收缩偶联的影响，并确定 嘌呤核苷腺苷发挥作用的机制-- 公认的对缺血后心脏功能的有益影响。更改后的 顿抑心肌的兴奋-收缩耦合被认为是由于 改变心肌能量，收缩蛋白功能障碍，和/或 瞬时钙离子引起的细胞内钙离子处理的改变 超载。临床上已有心肌顿抑的病例记录。 急性冠脉搭桥术后溶栓治疗 心肌梗死。因此，建议的实验是临床上的。 与人类缺血性疾病相关的和潜在的治疗相关性 心脏病。大鼠心肌顿抑的影响及对其的影响 腺苷治疗将在活体猪区域进行 心肌缺血模型及正常和顿抑分离的心肌细胞 心肌。拟议研究的具体目标是：(1) 测定活体心肌顿抑和瞬时钙的影响 超负荷对心肌能量学与基础和超负荷关系的影响 刺激心肌收缩能力。预处理剂处理的效果 腺苷或与腺苷A1受体激动剂和拮抗剂联用 心肌的磷酸化潜力和变力储备将 评估过了。(2)确定腺苷是否引起心肌细胞的衰减。 心肌顿抑与肌原纤维正常化有关 收缩特性。张力-主成分分析和主成分分析 最大缩短速度(Vmax)将在蒙皮中确定 从活体顿抑猪心肌和正常猪心肌中分离的制剂。 在体内后将进行皮肤制剂的研究 用腺苷或腺苷A1受体激动剂或 对抗者。腺苷在细胞水平上作用的具体机制 肌丝将通过评估磷酸化状态来研究 粗(C-蛋白，肌球蛋白LC2)和细(TnT，TnT，TM)细丝蛋白 在不同的实验条件下。(3)确定是否 心肌顿抑与心肌细胞内钙离子变化相关 动态平衡。基础钙电流和刺激钙电流与细胞内游离钙 从正常和顿抑猪分离的心肌细胞将测定(Ca~(2+))i 心肌。我们在这里的主要兴趣是阐明 腺苷治疗对正常和顿抑心肌钙稳态的影响。

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.