Spontaneous relaxation of isolated smooth muscle cells shortened with muscarinic receptor stimulation

当收缩激动剂被移除时，收缩的平滑肌自发地松弛。在这项研究中，我们提供了第一个证据表明，毒蕈碱受体介导的激活PKC在乙酰胆碱诱导的细胞缩短的过程中是必要的，为随后的松弛缩短的细胞。本研究采用链溶素-O-通透的单个平滑肌细胞，在无张力负荷条件下测量细胞缩短，发现PKC依赖的舒张机制是特异性的毒蕈碱受体的收缩刺激。此外，受体介导的激活PKC的ACh诱导的细胞缩短的过程中所需的缩短的细胞的后续松弛。因此，可能需要PKC依赖性促进阶段才能实现随后的舒张，而舒张是由收缩刺激剂ACh的去除和游离Ca^2+的下降触发的。相反，Ca^<2+>诱导的细胞缩短的舒张作用不依赖于PKC。 ...更多信息 PKC依赖性的差异可能是由于毒蕈碱受体介导的代谢信号的激活。PKC依赖性促进舒张的机制尚不清楚。然而，最有可能的是，在激动剂诱导的收缩过程中，可能涉及PKC依赖性的调节机制激活。据报道，与维持音调和闩锁状态相关的几种可能的调节机制被PKC依赖性激活。我们关注其中一种机制，细胞骨架的重组。我们已经获得了一些证据表明，在收缩过程中，PKC调节肌动蛋白细胞骨架的重组是激动剂诱导的收缩随后松弛的原因，在张力负荷条件下收缩的平滑肌组织很容易被洗涤松弛，即使收缩是由ACh在蛋白激酶抑制剂的存在下诱导的。这些结果出现的可能性，PKC依赖的松弛机制，积极参与激动剂缩短的单个平滑肌细胞的松弛，显然是隐藏的张力相关的松弛在准备张力加载的整个tissues.In结论，我们证明了一种新的平滑肌松弛机制。这表明激动剂诱导的收缩过程中，PKC依赖的肌动蛋白细胞骨架重组促进自发性舒张。少

Contracted smooth muscle relaxs spontaneously when contractile agonist is removed. In this study, we have provide first evidence that muscarinic receptor-mediated activation of PKC in the process of ACh-induced cell shortening is necessary for the subsequent relaxation of the shortened cells. This study was done with streptolysin-O-permeabilized single smooth muscle cells by measuring cell shortening under the condition without any tension load.PKC-dependent relaxation mechanism was found to be specific for the contractile stimulation of muscarinic receptors. Moreover, the receptor-mediated activation of PKC in the process of ACh-induced cell shortening was required for the subsequent relaxation of the shortened cells. Thus, it is likely that PKC-dependent promotion stage is required for the subsequent relaxation which is triggered by removal of contractile stimulant ACh and fall of free Ca^<2+>. In contrast, the relaxation from Ca^<2+>-induced cell shortening was independent on PKC.Th … More e differences in PKC-dependence could be due to the activation of muscarinic receptor-mediated metabotropic signaling.It is unclear what is the mechanism underlying PKC-dependent promotion of relaxation. It is, however, most likely that PKC-dependent activation of regulatory mechanisms during agonist-induced contractions could be involved. Several possible regulatory mechanisms which are related to maintenance of tone and latch state are reported to be activated PKC-dependently. We focused one of these mechanisms, the reorganization of cytoskeleton. We have obtained several evidences that PKC regulation of actin cytoskeletal reorganization during contraction is responsible for subsequent relaxation from agonist-induced contraction.Contracted smooth muscle tissues under the condition with tension-load were readily relaxd by a wash even if the contraction was induced by ACh in the presence of a protein kinase inhibitor. These results arise the possibility that the PKC-dependent relaxation mechanism, which actively participates in the relaxation of agonist-shortened individual smooth muscle cells, is apparently concealed by the tension-related relaxation in the preparation of tension-loaded whole tissues.In conclusion, we demonstrated a novel mechanism of smooth muscle relaxation. It is suggested that PKC-dependent reorganization of actin cytoskeleton during agonist-induced contraction promotes spontaneous relaxation. Less