Ca2+ regulates the kinetics of tension development in intact cardiac muscle.
Ca2+ regulates the kinetics of tension development in intact cardiac muscle.
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Ca2 调节完整心肌张力发展的动力学。
DOI：
10.1152/ajpheart.1998.275.3.h744
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Camacho,SA
中科院分区：
文献类型：
--
作者：
Baker,AJ;Figueredo,VM;Keung,EC;Camacho,SA
这项研究的目的是确定钙离子是否在调节完整心肌张力发育动力学中起作用。在心肌中，这一钙离子调节的基本问题一直存在争议。方法是在22℃下，用不同的外钙离子浓度([Ca~(2+)])诱导大鼠完整右室心肌小梁的稳态强直性收缩。在强直性收缩过程中，横桥被机械破坏，张力再发展的动力学由指数张力再发展(KTR)的速率常数来评估。肌张力与外源[Ca~(2+)]的关系类似于张力与[Ca~(2+)]的关系。强直性最大张力(饱和胞浆[Ca~(2+)])时，K_(Trr)为16.4±2.2 S−_1(平均值±SE，n=7)，零张力(低胞浆[Ca~(2+)])时，K_(Trr)为最大值的20%(3.3±0.7 S−_1)。使用不同的力学方案破坏跨桥得到了定性相似的结果。这些数据表明，完整心肌的张力重建动力学受钙激活水平的影响。这些发现与之前一项关于完整心肌的研究结果形成了对比。在体心动周期中，张力发育动力学的激活依赖性可能在决定心肌张力升高的速度和幅度中起重要作用。
The goal of this study was to determine whether Ca2+plays a role in regulating tension development kinetics in intact cardiac muscle. In cardiac muscle, this fundamental issue of Ca2+regulation has been controversial. The approach was to induce steady-state tetanic contractions of intact right ventricular trabeculae from rat hearts at varying external Ca2+concentrations ([Ca2+]) at 22°C. During tetani, cross bridges were mechanically disrupted and the kinetics of tension redevelopment were assessed from the rate constant of exponential tension redevelopment (ktr). There was a relationship betweenktrand external [Ca2+] that was similar in form to the relationship between tension and [Ca2+]. Thus a close relationship also existed betweenktrand tension (r= 0.88;P< 0.001); whereas at maximal tetanic tension (saturating cytosolic [Ca2+]),ktrwas 16.4 ± 2.2 s−1(mean ± SE,n= 7), at zero tension (low cytosolic [Ca2+]),ktrextrapolated to 20% of maximum (3.3 ± 0.7 s−1). Qualitatively similar results were obtained using different mechanical protocols to disrupt cross bridges. These data demonstrate that tension redevelopment kinetics in intact cardiac muscle are influenced by the level of Ca2+activation. These findings contrast with the findings of one previous study of intact cardiac muscle. Activation dependence of tension development kinetics may play an important role in determining the rate and extent of myocardial tension rise during the cardiac cycle in vivo.