CONTROL OF METABOLISM BY NO IN THE FAILING HEART

越来越多的研究支持NO在心脏代谢控制中的作用。我们最近发现，在正常犬的NO合成酶（NOS）的急性封锁和起搏诱导的心力衰竭过程中NO的生产下降都与开关从游离脂肪酸（FFA）的碳水化合物的利用心脏。这些现象背后的机制尚不清楚。这项研究计划将确定NO在控制心脏底物利用中的作用，以及这种作用是否在心力衰竭期间丧失。第一个具体目标是确定NO是否控制心脏FFA和碳水化合物代谢。通过输注同位素标记的FFA、葡萄糖和乳酸盐，在清醒犬中测量NOS阻断前后心脏中FFA和碳水化合物氧化的速率。在体内实验结束时，将在冷冻夹闭的心脏活检组织中测量标记底物蓄积以及碳水化合物和FFA氧化关键酶的活性。组织的快速冷冻将保持酶从体内到体外的活化状态。第二个具体目标是确定心力衰竭期间发生的心肌代谢和生化变化是否与正常心脏中NOS阻断后发现的变化相似，以及它们是否可以被NO释放剂逆转。将采用相同的体内和体外方法。通过慢性起搏在犬中诱导心力衰竭。第三个具体目标是确定急性动脉底物浓度的变化是否会影响心力衰竭期间的心脏耗氧量，以及这种影响是否可以通过NO释放剂逆转。我们的初步数据表明，FFA消耗可以导致心脏耗氧量增加无关的血流动力学的变化，但只有当NO是不存在的。这些研究将阐明NO在心力衰竭病理生理学中的作用。这也将为NO供体治疗心力衰竭提供新的药理学机制。基于这些药剂对心脏代谢的直接控制。

A role for NO in the control of cardiac metabolism is receiving support from an increasing number of studies. We recently found that the acute blockade of NO synthase (NOS) in normal dogs and the fall in NO production during pacing induced heart failure are both associated with a switch from free fatty acids (FFA) to carbohydrate utilization by the heart. The mechanisms underlying these phenomena are unknown. This research proposal will determine the role of NO in the control of cardiac substrate utilization and whether this role is lost during heart failure. The first specific aim is to determine whether NO controls cardiac FFA and carbohydrate metabolism. The rate of FFA and carbohydrate oxidation in the heart, before and after NOS blockade, will be measured in conscious dogs by infusing isotope-labeled FFA, glucose and lactate. Labeled substrate accumulation and the activity of key enzymes for carbohydrate and FFA oxidation will be measured in cardiac biopsies freeze-clamped at the end of the in vivo experiment. The rapid freezing of the tissue will preserve the activation state of enzymes from in vivo to in vitro. The second specific aim is to determine whether the myocardial metabolic and biochemical alterations occurring during heart failure are similar to those found after NOS blockade in normal hearts and if they can be reversed by a NO-releasing agent. The same methods in vivo and in vitro will be employed. Heart failure will be induced in dogs by chronic pacing. The third specific aim is to determine whether acute alterations of arterial substrate concentration can affect cardiac oxygen consumption during heart failure and if this effect can be reversed by NO-releasing agents. Our preliminary data indicate that FFA consumption can cause increased in cardiac O2 consumption unrelated to hemodynamic changes, but only when NO is absent. These studies will elucidate the role of NO in the pathophysiology of heart failure. This will also provide a new pharmacological mechanism of NO-donors in the treatment of heart failure. based on direct control by these agents on cardiac metabolism.