CULTURED CARDIAC MYOCYTES--A MODEL OF IRON OVERLOAD

血色病心肌铁毒性机制的探讨 由于缺乏合适的实验模型， 我们 目的是研究铁负载和螯合作用对体外 培养的大鼠心肌细胞的搏动系统。 铁在这些负载 细胞导致收缩性和自律性受损，由铁逆转 螯合作用 拟议研究的目的是表征 铁毒性导致肌细胞功能受损的机制， 可以防止或改变的条件。 铁的影响 加载将沿沿着3条线进行研究：I. 铁的吸收机制 心肌细胞：铁浓度、温度和 代谢抑制剂;铁摄取对转铁蛋白受体的依赖性 铁螯合剂对细胞内分布的影响 和铁的动员。 二. 铁负载量对膜的影响 结构： 丙二炔二醛形成反映自由基诱导 脂质过氧化;磷脂，溶血磷脂，磷脂酰 分离的肌膜中乙醇胺/磷脂酰胆碱的比例; 膜结构的改变反映在细胞膜的分布上， 与细胞外介质接触的膜脂质部分， 通过放射性碘标记技术鉴定。 三. 铁负荷对 肌细胞收缩力、动作电位和钙摄取;原发性 使用药物中和的药理生理学研究定义的损伤 铁的负性肌力作用。 在所有3个中测试的变量 培养阶段包括培养基组成、铁毒性的改良 通过共存缺氧，抗坏血酸，α-生育酚和其他 抗氧化剂和铁螯合药物的能力，以防止或逆转 铁毒性 从这些研究中获得的信息可能有助于 了解急性铁毒性的机制，以及 慢性铁中毒导致临床心肌病 与铁超载有关，铁螯合的方式 试剂、自由基清除剂和抗氧化剂可以防止或改变 铁损伤的严重程度。 这些信息可能有助于 制定更合理的输血管理方法 地中海贫血和其他铁负荷性贫血中的铁超负荷。

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.