Berman M R, Peterson J N, Yue D T, Hunter W C
Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205.
J Mol Cell Cardiol. 1988 May;20(5):415-26. doi: 10.1016/s0022-2828(88)80133-0.
To determine whether catecholamines produce alterations in myocardial myosin-actin cycling kinetics, we investigated the effects of isoproterenol upon mechanical characteristics of constantly activated heart muscle thought to reflect crossbridge behavior. In isolated rabbit right ventricular papillary muscles in barium contracture at 24 degrees C, we found that 10 microM isoproterenol caused: (a) a 23% reduction of the 10 to 90% rise time of slow tension recovery in force transients induced by rapid, small amplitude stretches; and (b) a 23% increase in the frequency of sinusoidal length perturbation at which stiffness amplitude exhibited a minimum. Based upon previous mechanistic interpretations of force transients, and on an analysis developed here to relate crossbridge events to the frequency-dependence of stiffness, we argue that our observations provide evidence that isoproterenol induces an acceleration of crossbridge cycling rate. This raises the intriguing prospect that beta-adrenergic stimulation regulates contraction, not only by well-known alterations in calcium metabolism, but also by intrinsic modulation of the force-generating machinery itself.
为了确定儿茶酚胺是否会改变心肌肌球蛋白 - 肌动蛋白循环动力学，我们研究了异丙肾上腺素对持续激活的心肌机械特性的影响，这种心肌机械特性被认为反映了横桥行为。在24℃下处于钡收缩状态的离体兔右心室乳头肌中，我们发现10微摩尔异丙肾上腺素会导致：（a）由快速小幅度拉伸诱发的力瞬变中，缓慢张力恢复的10%至90%上升时间缩短23%；（b）在正弦长度微扰频率下，刚度振幅出现最小值时的频率增加23%。基于先前对力瞬变的机理解释，以及在此处建立的将横桥事件与刚度频率依赖性相关联的分析，我们认为我们的观察结果提供了证据，表明异丙肾上腺素可诱导横桥循环速率加快。这就引发了一个有趣的前景，即β - 肾上腺素能刺激不仅通过众所周知的钙代谢改变来调节收缩，还通过对产生力的机制本身进行内在调节来实现。
