ALTERED FORCE KINETICS IN NORMAL AND STRESSED HEARTS

心室肌球蛋白的不同同工酶已被报道， 哺乳动物心脏 在某些种属（大鼠、家兔）中，心肌 性能与心室异肌球蛋白的差异相关， 格局 一些调查人员提出了这样一种可能性， 心肌性能和异肌球蛋白模式相关， 不同肌群的过桥骑行特征不同， 异肌球蛋白。 这项研究的目的是调查 过桥循环特征的异肌球蛋白依赖性。 小梁， 从老鼠的心脏中提取，这些老鼠的心脏主要是V1或V2。 肌球蛋白V3同种型，将被化学剥皮（以允许精确的 肌原纤维离子环境的实验控制）和 在等长收缩中被激活 在等长力的平台 将应用小幅度的快速长度变化， 将记录力瞬变。 肌肉会被保留下来 随后通过凝胶测定它们异肌球蛋白模式 电泳 我们将测试力瞬变是否反映 通过调查的影响， 温度和底物（MgATP）浓度对特性的影响 临时居民 信息关于Crossbridge骑自行车的特点， 将得到具有不同肌球蛋白同工酶模式极端的肌肉 从力的几个阶段的振幅和时间进程 瞬态响应;该信息将通过拟合 力瞬变的指数。 这项研究的结果将 提供关于肌球蛋白同工酶类型对 肌球蛋白与肌球蛋白相互作用的基本力的动力学 肌动蛋白。 此外，这些结果可能有助于解释 在具有改变的应激适应心肌中观察到的性能变化 肌球蛋白同工酶谱

Different isoenzymes of ventricular myosin have been reported in the mammalian heart. In some species (rat, rabbit) differences in myocardial performance have been correlated with differences in ventricular isomyosin pattern. Several investigators have suggested the possibility that myocardial performance and isomyosin pattern are correlated because crossbridge cycling characteristics are different in muscles with different isomyosins. The objective of the proposed research is to investigate the isomyosin dependence of crossbridge cycling characteristics. Trabeculae, taken from rats treated so that their hearts have mostly either the V1 or the V3 isoform of myosin, will be chemically skinned (to allow precise experimental control of the ionic environment of the myofibrils) and activated in an isometric contraction. At the plateau of isometric force small amplitude rapid length changes will be applied and the resulting force transients will be recorded. The muscles will be saved for subsequent determination of their isomyosin patterns by gel electrophoresis. We will test whether the force transients reflect crossbridge cycling characteristics by investigating the effects of temperature and substrate (MgATP) concentration on the characteristics of the transients. Information about crossbridge cycling characteristics in muscles with different extremes of myosin isoenzyme pattern will be derived from the amplitudes and time courses of the several phases of the force transient response; this information will be extracted by fitting sums of exponentials to the force transients. The results of this research will provide information concerning the influence of myosin isoenzyme type on the kinetics of the fundamental force generating interaction of myosin with actin. In addition, these results may be helpful in explaining the performance changes observed in stress-adapted myocardium with altered myosin isoenzyme patterns.