CULTURED CARDIAC MYOCYTES--A MODEL OF IRON OVERLOAD

血色沉着症心肌铁中毒的机制探讨 由于缺乏合适的实验模型而严重受阻。我们 目的：研究铁负载和络合作用对体外血管紧张素转换酶的影响。 培养的大鼠心肌细胞搏动系统。这里面装的是铁 细胞的收缩和自律性受损，被铁逆转 络合作用。拟议研究的目标是描述 铁中毒导致心肌细胞功能受损的机制 可以防止或改变的条件。铁的作用 负荷将沿着三条线进行研究：I.铁吸收的机制 心肌细胞：铁浓度、温度和钙离子浓度的影响 代谢抑制剂；铁摄取对转铁蛋白受体的依赖性 铁络合剂对细胞内分布的影响 和铁的动员。铁负荷对膜的影响 结构：丙二醛的形成反映了自由基的诱导 脂质过氧化；磷脂、溶血磷脂、磷脂 肌膜乙醇胺/磷脂酰胆碱比值； 膜结构的变化反映在分布上 与细胞外介质AS接触的膜脂部分 通过放射性碘化技术进行鉴定。三、铁负荷对人体健康的影响 心肌细胞收缩、动作电位和钙摄取；原发部位 使用药物中和的药物生理学研究定义的损伤 铁的负肌力作用。要在所有3个项目中测试的变量 阶段包括培养基组分、铁毒性的修饰 由共存的低氧、抗坏血酸、α-生育酚等 抗氧化剂，以及铁螯合药物预防或逆转的能力 铁中毒。从这些研究中获得的信息可能有助于 了解急性铁中毒的机制，而不是直接了解 慢性铁中毒导致临床条件下的心肌病 与铁超载有关，以及铁的螯合方式 试剂、自由基清除剂和抗氧化剂可以防止或改变 铁引起的损伤的严重性。这些信息可能会对 发展一种更合理的输液管理方法 地中海贫血和其他铁负荷贫血的铁负荷过高。

Understanding the mechanism of myocardial iron toxicity in hemochromatosis is seriously hindered by the lack of an appropriate experimental model. We intend to study the effects of iron loading and chelation on an in vitro system of beating rat cardiac myocytes in culture. Iron loading in these cells results in impaired contractility and automaticity, reversed by iron chelation. The objective of the proposed studies is to characterize the mechanism of iron toxicity resulting in impaired myocyte function, and the conditions whereby it may be prevented or modified. The effect of iron loading will be studied along 3 lines: I. Mechanism of iron uptake by myocardial cells: the effect of iron concentration, temperature and metabolic inhibitors; dependence of iron uptake on transferrin receptor synthesis, and; the effect of iron chelators on intracellular distribution and mobilization of iron. II. Effect of iron loading on membrane structure: maloynldialdehyde formation reflecting free-radical induced lipid peroxidation; phospholipid, lysophospholipid, phosphatidyl ethanolamine/phosphatidyl choline ratio in the isolated sarcolemma; alterations in membrane architecture reflected in the distribution of membrane lipid moieties in contact with the extracellular medium as identified by a radioiodination technique. III. Effect of iron loading on myocyte contractility, action potential and calcium uptake; site of primary injury defined by pharmacophysiologic studies employing drugs neutralizing the negative inotropic effect of iron. Variables to be tested in all 3 phases include composition of culture medium, modification of iron toxicity by coexistent hypoxia, ascorbic acid, alpha tocopherol and other antioxidants, and the ability of iron chelating drugs to prevent or reverse iron toxicity. Information gained in these studies may help in understanding the mechanism of acute iron toxicity and, less directly, of chronic iron toxicity resulting in myocardiopathy in clinical conditions associated with iron overload, and the manner in which iron chelating agents, free radical scavengers and antioxidants may prevent or modify the severity of iron induced damage. Such information may be helpful in the developmnet of a more rational approach to the management of transfusional iron overload in thalassemia and other iron loading anemias.