Isometric Relaxation of Rat Myocardium atEnd‐Systolic Fiber Length
Isometric Relaxation of Rat Myocardium atEnd‐Systolic Fiber Length
复制标题
大鼠心肌收缩末期纤维长度的等长舒张
DOI：
10.1161/01.res.43.6.865
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发表时间：
1978
影响因子：
20.1
通讯作者：
O. H. Bing
中科院分区：
文献类型：
--
作者：
A. Wiegner;O. H. Bing
在生理顺序收缩(PSC)中，以与完整心脏相似的方式加载分离的肌肉准备，等长松弛先于等张松弛，并且发生在最小(收缩末期)长度。我们研究了初始肌长、负荷、温度、钙和异丙肾上腺素对生理顺序收缩等长松弛相的影响，以确定大鼠左室心肌等长松弛速率的决定因素。在基线温度(28℃)下，松弛是非指数的，并且使用最大力衰减率(-df/dtma，)来评估松弛的变化。三个因素，缩短，收缩末期长度，和总负荷，被检查为可能的−df/dtmax的机械决定因素。我们发现，−df/dtmax与收缩末期肌长在94%以下的L--x呈线性相关；−df/dtmax也与总负荷密切相关，但在负荷约为峰值发育力的80%时达到峰值，此后下降。短轴缩短率与−、df/dtmax的相关性较差。−df/dtma‘与收缩末期长度关系的线性部分的斜率似乎与肌肉负荷条件无关，并且对已知的改变松弛的因素很敏感。
In a ‘physiologically sequenced’ contraction (PSC), which loads the isolated muscle preparation in a manner which approximates that of the intact heart, isometric relaxation precedes isotonic relaxation and occurs at minimum (‘end-systolic’) length. We studied the effects of initial muscle length, load, temperature, calcium, and isoproterenol on the isometric relaxation phase of physiologically sequenced contractions to define the determinants of the rate of isometric relaxation of rat left ventricular myocardium. At the baseline temperature (28 °C), relaxation was found to be nonexponential, and the maximum rate of decline of force (-dF/dtma,) was used to evaluate changes in relaxation. Three factors, shortening, end-systolic length, and total load, were examined as possible mechanical determinants of −dF/dtmax. We found that −dF/dtmax is linearly related to end-systolic muscle length for lengths below 94% of L--,x; −dF/dtmax is also strongly related to total load for lightly loaded contractions, but peaks at loads of approximately 80% of peak developed force and declines thereafter. Shortening is poorly correlated with −dF/dtmax. The slope of the linear portion of the relation between −dF/dtma′ and end-systolic length appears to be independent of muscle-loading conditions, and sensitive to factors known to alter relaxation.