Evaluation of the cross-bridge-dependent change in the Ca2+ affinity of troponin C in aequorin-injected ferret ventricular muscles
Evaluation of the cross-bridge-dependent change in the Ca2+ affinity of troponin C in aequorin-injected ferret ventricular muscles
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DOI：
10.1016/j.ceca.2004.08.003
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发表时间：
2005-02-01
期刊：
影响因子：
4
通讯作者：
Kurihara, S
中科院分区：
文献类型：
--
作者：
Ishikawa, T;O-Uchi, J;Kurihara, S
心肌肌钙蛋白C （TnC）的Ca2+亲和力受活性交叉桥（下游依赖机制）的调节。在本研究中，我们展示了一种方法来评估TnC在收缩过程中Ca2+亲和力的下游依赖变化，使用注射雪貂乳头肌。为此，在各种条件下测量了额外Ca2+的张力依赖性变化（细胞内Ca2+浓度的短暂增加（[Ca2+](i)），以响应快速长度减少）。我们检查了张力降低的幅度和标准化的额外Ca2+的幅度之间的回归线（额外Ca2+除以[Ca2+](i)在长度变化之前）（标准化的额外Ca2+-张力关系）在抽搐收缩可以用于估计下游依赖的变化在TnC的Ca2+亲和力。EMD 57033 (EMD)（一种Ca2+敏化剂）和溶液中Ca2+浓度（[Ca2+](o)）的增加以浓度依赖的方式使标准化的额外Ca2+张力关系变浅。然而，2,3-丁二酮单肟（BDM）（脱敏剂之一）以浓度依赖的方式拮抗EMD和高[Ca2+](o)的影响。这些影响也被观察到EMD和BDM在破伤风收缩的标准化ca2 +张力关系。在强直收缩时，收缩前初始肌长缩短，使归一化的钙离子张力关系变得陡峭。较高的[Ca2+](o)和EMD可使抽动收缩的长度-张力关系显著上移，而BDM则呈浓度依赖性作用。因此，在完整心肌中具有生理功能的TnC的Ca2+亲和力的下游依赖性变化可以使用标准化的额外Ca2+张力关系来评估。(C) 2004 Elsevier Ltd.版权所有。
Ca2+ affinity of cardiac troponin C (TnC) is regulated by the active cross-bridges (downstream-dependent mechanism). In the present study, we showed one of the methods to evaluate the downstream-dependent change in the Ca2+ affinity of TnC during contraction using the aequorin-injected ferret papillary muscle. For this purpose, the tension-dependent change in the extra-Ca2+ (a transient increase in the intracellular Ca2+ concentration ([Ca2+](i)) in response to a quick length reduction) was measured under various conditions. We examined whether the regression line between the magnitude of tension reduction and the magnitude of the normalized extra-Ca2+ (the extra-Ca2+ was divided by [Ca2+](i) immediately before length change) (the normalized extra-Ca2+-tension relation) in twitch contraction can be used for the estimation of the downstream-dependent change in the Ca2+ affinity of TnC. The normalized extra-Ca2+-tension relation became shallow by EMD 57033 (EMD) (one of the Ca2+ sensitizers) and by an increase in Ca2+ concentration in the solution ([Ca2+](o)) in a concentration-dependent manner. However, 2,3-butanedione monoxime (BDM) (one of the desensitizers) antagonized the effects of EMD and higher [Ca2+](o) in a concentration-dependent manner. These effects of EMD and BDM were also observed in the normalized extra-Ca2+-tension relation in tetanic contraction. The normalized extra-Ca2+-tension relation became steep by shortening the initial muscle length before contraction in tetanic contraction. Length-tension relation in twitch contraction was significantly shifted upward by higher [Ca2+](o) and EMD, but BDM showed the opposite effects on them in a concentration-dependent manner. Thus, the downstream-dependent change in the Ca2+ affinity of TnC which physiologically functions in intact cardiac muscle can be evaluated using the normalized extra-Ca2+-tension relation. (C) 2004 Elsevier Ltd. All rights reserved.