LENGTH, FORCE, AND CA2+-TROPONIN-C AFFINITY IN CARDIAC AND SLOW SKELETAL-MUSCLE
LENGTH, FORCE, AND CA2+-TROPONIN-C AFFINITY IN CARDIAC AND SLOW SKELETAL-MUSCLE
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DOI：
10.1152/ajpcell.1994.266.4.c1077
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发表时间：
1994-04-01
影响因子：
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通讯作者：
FUCHS, F
中科院分区：
文献类型：
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作者：
WANG, YP;FUCHS, F
肌钙蛋白 C 有两种同工型，一种 (sTnC) 在快骨骼肌中表达，另一种 (cTnC) 在心肌和慢速骨骼肌中表达。基于亚基交换实验，表明 cTnC 可能作为长度传感分子发挥特定作用。在这项研究中，我们比较了牛心室和慢兔比目鱼肌的去皮纤维，比较了力和肌节长度对 Ca2+ 与肌钙蛋白 C 结合的影响。双同位素技术用于测量与力产生同时发生的 Ca2+ 结合。磷酸盐类似物钒酸盐用于调节力，与游离 Ca2+ 浓度无关。为了确定肌节长度的影响，将肌纤维从较长的肌节长度释放到较短的肌节长度，并在释放之前或之后测定结合的Ca2+。力量或长度的减少与心肌中 Ca2+ 与 cTnC 的结合减少有关，但在比目鱼肌中没有看到这些干预措施的影响。因此，调节 Ca2+ 结合位点上的机械反馈的性质似乎是肌丝系统的特性，而不是肌钙蛋白 C 亚型的特性。
Troponin C occurs as two isoforms, one (sTnC) expressed in fast skeletal muscle and the other (cTnC) expressed in cardiac and slow skeletal muscle. On the basis of subunit exchange experiments it has been suggested that cTnC may play a specific role as a length-sensing molecule. In this study we have compared skinned fibers from bovine ventricle and slow rabbit soleus muscle with respect to the effects of force and sarcomere length on Ca2+ binding to troponin C. A double-isotope technique was used to measure Ca2+ binding concurrent with force generation. The phosphate analogue vanadate was used to regulate force independent of free Ca2+ concentration. To determine the effect of sarcomere length, muscle fibers were released from longer sarcomere length to shorter sarcomere length, and bound Ca2+ was determined either before or after the release. Reduction in force or length was associated with reduced binding of Ca2+ to cTnC in cardiac muscle, but no effect of these interventions was seen in soleus muscle. Thus the nature of the mechanical feedback on the regulatory Ca2+-binding sites appears to be a property of the myofilament system rather than the troponin C isoform.