PASSIVE TENSION IN CARDIAC-MUSCLE - CONTRIBUTION OF COLLAGEN, TITIN, MICROTUBULES, AND INTERMEDIATE FILAMENTS
PASSIVE TENSION IN CARDIAC-MUSCLE - CONTRIBUTION OF COLLAGEN, TITIN, MICROTUBULES, AND INTERMEDIATE FILAMENTS
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DOI：
10.1016/s0006-3495(95)80278-x
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发表时间：
1995-03-01
影响因子：
3.4
通讯作者：
IRVING, TC
中科院分区：
文献类型：
--
作者：
GRANZIER, HL;IRVING, TC
通过研究被动（或未激活）的单个肌细胞和小梁来研究大鼠心肌的被动张力-肌节长度关系。通过测量（1）KCl/Kl 提取对小梁和单个肌细胞的影响，（2）胰蛋白酶消化对单个肌细胞的影响，以及（3）秋水仙碱对单个肌细胞的影响，研究胶原蛋白、肌联蛋白、微管和中间丝对张力和硬度的贡献。研究发现，在心脏肌节的工作范围内（长度类似于1.9-2.2μm），胶原蛋白和肌联蛋白是被动张力的最重要贡献者，肌联蛋白在工作范围的较短端占主导地位，而胶原蛋白在较长长度上占主导地位。微管对某些细胞的被动张力贡献不大，但平均而言，它们的贡献并不显着。最后，在肌节长度从1.9到2.1μm之间，中间丝对小梁被动张力的贡献约为10%，而在更长的长度上，它们的贡献仅下降到百分之几。在心脏的生理肌节长度处，心脏肌联蛋白比同等长度的骨骼肌肌联蛋白产生更高的张力（>20倍）。这可能与心脏肌动蛋白的分子量为 2.5 MDa 的发现有关，比哺乳动物骨骼肌的肌动蛋白小 0.3-0.5 MDa，预计这会导致心肌 I 带中的可延伸肌动蛋白片段更短。绘制的被动应力与可伸展肌蛋白片段应变的关系表明，心肌和骨骼肌中的应力-应变关系相似。心肌和骨骼肌之间在肌节水平上的被动应力差异主要是由于给定肌节长度下心肌肌联 I 段的应变更高。通过表达较小的肌联蛋白亚型，而不改变分子本身的特性，心肌能够在生理肌节长度上产生显着水平的被动张力。
The passive tension-sarcomere length relation of rat cardiac muscle was investigated by studying passive (or not activated) single myocytes and trabeculae. The contribution of collagen, titin, microtubules, and intermediate filaments to tension and stiffness was investigated by measuring (1) the effects of KCl/Kl extraction on both trabeculae and single myocytes, (2) the effect of trypsin digestion on single myocytes, and (3) the effect of colchicine on single myocytes. It was found that over the working range of sarcomeres in the heart (lengths similar to 1.9-2.2 mu m), collagen and titin are the most important contributors to passive tension with titin dominating at the shorter end of the working range and collagen at longer lengths. Microtubules made a modest contribution to passive tension in some cells, but on average their contribution was not significant. Finally, intermediate filaments contributed about 10% to passive tension of trabeculae at sarcomere lengths from similar to 1.9 to 2.1 mu m, and their contribution dropped to only a few percent at longer lengths. At physiological sarcomere lengths of the heart, cardiac titin developed much higher tensions (>20-fold) than did skeletal muscle titin at comparable lengths. This might be related to the finding that cardiac titin has a molecular mass of 2.5 MDa, 0.3-0.5 MDa smaller than titin of mammalian skeletal muscle, which is predicted to result in a much shorter extensible titin segment in the I-band of cardiac muscle. Passive stress plotted versus the strain of the extensible titin segment showed that the stress-strain relationships are similar in cardiac and skeletal muscle. The difference in passive stress between cardiac and skeletal muscle at the sarcomere level predominantly resulted from much higher strains of the I-segment of cardiac titin at a given sarcomere length. By expressing a smaller titin isoform, without changing the properties of the molecule itself, cardiac muscle is able to develop significant levels of passive tension at physiological sarcomere lengths.