Unloaded shortening increases peak of Ca2+ transients but accelerates their decay in rat single cardiac myocytes
Unloaded shortening increases peak of Ca2+ transients but accelerates their decay in rat single cardiac myocytes
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DOI：
10.1152/ajpheart.00012.2003
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发表时间：
2003-08-01
影响因子：
4.8
通讯作者：
Sugi, H
中科院分区：
文献类型：
--
作者：
Yasuda, S;Sugiura, S;Sugi, H
研究细胞内钙离子浓度([Ca~(2+)](I))(钙瞬变)的时间依赖性变化与单个心肌细胞机械活动之间的关系，对于了解心脏功能的调节机制具有重要意义。然而，由于用单个心肌细胞进行机械测量的技术困难，同时记录钙瞬变和机械活动主要是用多细胞心脏制剂进行的，这给出了关于等长抽动和无负荷缩短性抽动期间的钙瞬变的相互矛盾的结果。在本研究中，我们将细胞内钙离子测量光学系统与使用碳纤维的测力系统相结合，以研究在大范围负荷下，钙瞬变与大鼠单个心肌细胞机械活动之间的关系。为了最大限度地减少肌浆网钙负荷的负荷依赖性，肌浆网的收缩模式在每次抽动时都从无负荷缩短转换为等长收缩。在无负荷缩短的抽动中，钙瞬变表现出比等长抽动时更高的峰值和更高的衰减率。同样，当我们改变每对抽搐的收缩模式时，钙瞬变只取决于收缩模式。机械解偶联与2，3-丁二酮单肟消除了这种对收缩模式的依赖。我们的结果表明，钙瞬变反映了肌钙蛋白C对钙离子的亲和力，这种亲和力受细丝上应变的变化而不是长度变化本身的影响。
It is of paramount importance to investigate the relation between the time-dependent change in intracellular Ca2+ concentration ([Ca2+](i)) (Ca2+ transients) and the mechanical activity of isolated single myocytes to understand the regulatory mechanisms of heart function. However, because of technical difficulties in performing mechanical measurements with single myocytes, the simultaneous recording of Ca2+ transients and mechanical activity has mainly been performed with multicellular cardiac preparations that give conflicting results concerning Ca2+ transients during isometric twitches and during twitches with unloaded shortening. In the present study, we coupled intracellular Ca2+ measurement optics with a force measurement system using carbon fibers to examine the relation between Ca2+ transients and the mechanical activity of rat single ventricular myocytes over a wide range of load. To minimize the possible load dependence of sarcoplasmic reticulum Ca2+ loading, contraction mode was switched at every twitch from unloaded shortening to isometric contraction. During a twitch with unloaded shortening, the Ca2+ transients exhibited a higher peak and a higher rate of decay than transients during an isometric twitch. Similarly, when we changed the contraction mode in every pair of twitches, Ca2+ transients were dependent only on the mode of contraction. Mechanical uncoupling with 2,3-butanedione monoxime abolished this dependence on the mode of contraction. Our results suggest that Ca2+ transients reflect the affinity of troponin C for Ca2+, which is influenced by the change in strain on the thin filament but not by the length change per se.