Substitution of cardiac troponin C into rabbit muscle does not alter the length dependence of Ca2+ sensitivity of tension.
Substitution of cardiac troponin C into rabbit muscle does not alter the length dependence of Ca2+ sensitivity of tension.
复制标题
将心肌肌钙蛋白 C 替换至兔肌肉中不会改变张力的 Ca2 敏感性的长度依赖性。
DOI：
10.1113/jphysiol.1991.sp018708
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Greaser,ML
中科院分区：
文献类型：
--
作者：
Moss,RL;Nwoye,LO;Greaser,ML
1.在肌节长度的生理范围内，心肌的长度-张力关系一般比骨骼肌陡峭。最近的研究表明，与骨骼肌钙蛋白C(STnC)相比，心肌肌钙蛋白C(CTNC)可能具有更大的张力钙敏感性随长度的变化。我们通过表征肌节平均长度为2.32微米和1.87微米的兔腰大肌肌纤维在cTNC部分替代内源性sTnC前后的张力-PCA(PCA IS-log[Ca+])关系来验证这一假设。2.在未经处理的对照纤维中，随着肌节长度的缩短，张力-PCA关系的中点(PCa50)向下移动0.15+/-0.02个PCA单位，即对Ca~(2+)的敏感性降低，关系变得更加陡峭。3.部分提取内源性sTnC和cTNC重组后，当cTNC重组完成95%以上时，pCa50的长度依赖性移位无明显变化，而当重组少于95%时，pCa50的长度依赖性移位显著增加。4.在部分提取sTnC的纤维中，也观察到pCa50的长度依赖移位增加，但随后没有重新添加cTNC。5.我们得出结论，仅有TNC类型的差异不足以解释骨骼肌和心肌在张力钙敏感性的长度依赖性上的差异。
1. The isometric length‐tension relationship for cardiac muscle is generally steeper than for skeletal muscle in the physiological range of sarcomere lengths. Recent studies suggest that cardiac troponin C (cTnC) may have intrinsic properties that confer greater length‐dependent changes in Ca2+ sensitivity of tension than for skeletal troponin C (sTnC). We tested this hypothesis by characterizing tension‐pCa (pCa is ‐log[Ca2+]) relationships in rabbit skinned psoas muscle fibres at mean sarcomere lengths of 2.32 and 1.87 microns both before and after partial replacement of endogenous sTnC with cTnC. 2. In untreated control fibres, the mid‐point (pCa50) of the tension‐pCa relationship shifted to lower pCa by 0.15 +/‐ 0.02 pCa units, i.e. became less sensitive to Ca2+, when sarcomere length was reduced, and the relationship became steeper. 3. Partial extraction of endogenous sTnC and reconstitution with cTnC resulted in no change in the length‐dependent shift of pCa50 when reconstitution with cTnC was more than 95% complete; however, when reconstitution was less than 95% complete, there were significant increases in the length‐dependent shift in pCa50. 4. An increase in the length‐dependent shift of pCa50 was also observed in fibres from which sTnC was partially extracted, but no cTnC was subsequently re‐added. 5. We conclude that differences in type of TnC alone are not sufficient to explain differences between skeletal and cardiac muscles in the length dependence of Ca2+ sensitivity of tension.
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DOI：
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期刊：
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