Bound calcium and force development in skinned cardiac muscle bundles: effect of sarcomere length.
Bound calcium and force development in skinned cardiac muscle bundles: effect of sarcomere length.
复制标题
带皮心肌束中的结合钙和力量发展：肌节长度的影响。
DOI：
10.1016/s0022-2828(88)80012-9
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发表时间：
1988
影响因子：
5
通讯作者：
Fuchs,F
中科院分区：
文献类型：
--
作者：
Hofmann,PA;Fuchs,F
有证据表明，心肌的力-长度曲线的陡峭上升肢（Frank-Starling关系）是基于肌丝Ca2+敏感性的长度依赖性。该实验室先前的工作表明，在肌节长度范围内，对应于心力长度曲线的上升肢（1.7至2.3 μm）， Ca2+-肌钙蛋白C的亲和力是长度依赖性的。在这项研究中，在atp诱导的肌节长度为2.2至2.4 μm和1.6至1.8 μm的纤维束产生力时，测量了Ca2+与化学剥皮的牛心肌束的结合。双同位素技术用于同时测定力-pCa和结合Ca2+-pCa关系。在较长的肌节长度上，纤维结合，在饱和时，相当于约3 mol Ca2+/mol肌钙蛋白c的Ca2+量。力的发展似乎与单个低亲和力Ca2+特异性位点的滴定相耦合。在pca 7.0 ~ 6.0范围内，肌节长度对Ca2+结合没有影响。在pca 6.0至5.0范围内，力急剧增加，除了相对力减少外，在较短的肌节长度处，结合Ca2+显著减少。因此，肌节长度似乎影响肌钙蛋白C调控位点的Ca2+结合特性。这些数据提供了直接证据，表明Ca2+-肌钙蛋白C亲和力的长度依赖性调节可能对心肌的力-长度关系做出了重要贡献。
There is evidence that the steep acending limb of the force-length curve in cardiac muscle (Frank-Starling relation) is based on a length-dependence of myofilament Ca2+sensitivity. Previous work from this laboratory has indicated that in the sarcomere length range corresponding to the ascending limb of the cardiac force length curve (1.7 to 2.3 μm) the Ca2+-troponin C affinity is length-dependent. In this study Ca2+binding to chemically skinned bovine cardiac muscle bundles was measured during ATP-induced force generation with fiber bundles having sarcomere lengths of 2.2 to 2.4 μm and 1.6 to 1.8 μm. A double isotope technique was used to make concurrent determinations of the force-pCa and bound Ca2+-pCa relationships. At the longer sarcomere lengths the fibers bound, at saturation, an amount of Ca2+equivalent to ∼3 mol Ca2+/mol troponin C. Force development appeared to be coupled to titration of the single, low-affinity Ca2+-specific site. In thepCa range 7.0 to 6.0 sarcomere length had no effect on Ca2+binding. In thepCa range 6.0 to 5.0, in which force increased steeply, there was, in addition to a decreased relative force, a significant reduction in bound Ca2+at the shorter sarcomere length. Thus sarcomere length appears to influence the Ca2+binding properties of the regulatory site on troponin C. These data provide direct evidence that length-dependent modulation of Ca2+-troponin C affinity may make a major contribution to the force-length relationship in cardiac muscle.