Role of contractile protein activation in the length-dependent modulation of tracheal smooth muscle force.
Role of contractile protein activation in the length-dependent modulation of tracheal smooth muscle force.
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收缩蛋白激活在气管平滑肌力长度依赖性调节中的作用。
DOI：
10.1152/ajpcell.1996.270.1.c243
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Gunst,SJ
中科院分区：
文献类型：
--
作者：
Mehta,D;Wu,MF;Gunst,SJ
肌肉产生的主动等距力在肌肉长度低于最佳长度（Lo）时减小。然而，当主动收缩肌肉的长度突然减少时，在力重建过程中所达到的等距力水平低于在较短长度处开始收缩时所达到的等距力水平。这归因于缩短引起的收缩蛋白失活。在这项研究中，测量了细胞内Ca2+和肌球蛋白轻链（MLC）磷酸化，以评估在等距收缩之前或期间改变平滑肌长度引起的等距力调节机制。等长力在Lo和0.5Lo之间的下降与乙酰胆碱或60 mM KCl引起的收缩期间MLC磷酸化和细胞内Ca2+的减少有关。收缩过程中肌肉的快速释放抑制了较短长度的力再开发，但不影响MLC磷酸化。我们得出的结论是，Ca(2+)-钙调素依赖的MLC磷酸化的减少显著地促进了长度低于Lo的等长力的下降，但与主动收缩的平滑肌快速释放相关的收缩性抑制并不是由缩短诱导的收缩蛋白失活引起的。
The active isometric force developed by a muscle decreases at muscle lengths below an optimal length (Lo). However, when the length of an actively contracting muscle is abruptly decreased, a lower level of isometric force is reached during force redevelopment than when the contraction is initiated at the shorter length. This has been attributed to a deactivation of contractile proteins caused by shortening. In this study, intracellular Ca2+ and myosin light chain (MLC) phosphorylation were measured to assess the mechanisms for the modulation of isometric force caused by changing smooth muscle length before or during isometric contraction. The decline in isometric force between Lo and 0.5Lo was associated with decreases in MLC phosphorylation and intracellular Ca2+ during contractions elicited by acetylcholine or 60 mM KCl. Quick release of the muscle during contraction depressed force redevelopment at the shorter length but not MLC phosphorylation. We conclude that decreases in Ca(2+)-calmodulin-dependent MLC phosphorylation contribute significantly to the decline in isometric force at lengths below Lo, but the depression of contractility associated with the quick release of actively contracted smooth muscle is not caused by a shortening-induced deactivation of contractile proteins.