Department of Physiology and Cell Biology, College of Medicine, Ohio State University, Columbus, OH.
J Gen Physiol. 2021 Jul 5;153(7). doi: 10.1085/jgp.202012829.
The two main phases of the mammalian cardiac cycle are contraction and relaxation; however, whether there is a connection between them in humans is not well understood. Routine exercise has been shown to improve cardiac function, morphology, and molecular signatures. Likewise, the acute and chronic changes that occur in the heart in response to injury, disease, and stress are well characterized, albeit not fully understood. In this study, we investigated how exercise and myocardial injury affect contraction-relaxation coupling. We retrospectively analyzed the correlation between the maximal speed of contraction and the maximal speed of relaxation of canine myocardium after receiving surgically induced myocardial infarction, followed by either sedentary recovery or exercise training for 10-12 wk. We used isolated right ventricular trabeculae, which were electrically paced at different lengths, frequencies, and with increasing β-adrenoceptor stimulation. In all conditions, contraction and relaxation were linearly correlated, irrespective of injury or training history. Based on these results and the available literature, we posit that contraction-relaxation coupling is a fundamental myocardial property that resides in the structural arrangement of proteins at the level of the sarcomere and that this may be regulated by the actions of cardiac myosin binding protein C (cMyBP-C) on actin and myosin.
哺乳动物心脏周期的两个主要阶段是收缩和舒张；然而，人类是否存在它们之间的联系尚不清楚。常规运动已被证明可以改善心脏功能、形态和分子特征。同样，心脏对损伤、疾病和应激的急性和慢性变化也得到了很好的描述，尽管还不完全了解。在这项研究中，我们研究了运动和心肌损伤如何影响收缩-舒张偶联。我们回顾性分析了接受手术诱导心肌梗死后，犬心肌收缩的最大速度与舒张的最大速度之间的相关性，随后进行 10-12 周的安静恢复或运动训练。我们使用电刺激不同长度、频率和β-肾上腺素能受体刺激的右心室肌小梁。在所有条件下，收缩和舒张都呈线性相关，无论是否有损伤或训练史。基于这些结果和现有文献，我们假设收缩-舒张偶联是一种基本的心肌特性，它存在于肌节水平的蛋白质结构排列中，并且可能受到肌球蛋白结合蛋白 C (cMyBP-C) 对肌动蛋白和肌球蛋白的作用的调节。
