ALTERED FORCE KINETICS IN NORMAL AND STRESSED HEARTS

心肌肌球蛋白的不同同工酶已被报道 哺乳动物的心脏。某些物种(大鼠、兔)在心肌组织中的差异 表现与脑室异肌球蛋白的差异有关 图案。一些调查人员提出了一种可能性，即 心肌功能和异肌球蛋白图谱相关，因为 不同类型肌肉的横桥自行车运动特征不同 异肌球蛋白。拟议研究的目的是调查 异肌球蛋白对交叉桥循环特性的依赖。小梁， 取自接受治疗的大鼠，使它们的心脏主要有V1或 肌球蛋白的V3异构体将被化学剥皮(以允许精确 对肌原纤维离子环境的实验控制)和 在等长收缩中被激活。在等轴力的平台上 将应用小幅度快速长度变化，并由此产生 将记录力量瞬变。肌肉将被保留下来，以备 凝胶随后测定它们的异肌球蛋白图谱 电泳法。我们将测试这些力的瞬变是否反映 跨桥骑行特性的调查研究 温度和底物(镁-三磷酸腺苷)浓度对其特性的影响 转瞬即逝的。有关跨桥骑行特性的信息，请参阅 肌球蛋白同工酶图谱的不同极端的肌肉将被衍生 从力的几个阶段的幅度和时间进程 瞬时响应；此信息将通过拟合以下各项之和来提取 力瞬变的指数。这项研究的结果将 提供有关肌球蛋白同工酶类型对 肌球蛋白与肌球蛋白基本力相互作用的动力学 肌动蛋白。此外，这些结果可能有助于解释 应激适应心肌功能改变的观察 肌球蛋白同工酶图谱。

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.