Regulation of gastrointestinal motility--insights from smooth muscle biology.
Regulation of gastrointestinal motility--insights from smooth muscle biology.
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DOI：
10.1038/nrgastro.2012.168
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发表时间：
2012-11
期刊：
影响因子：
--
通讯作者：
Ward SM
中科院分区：
文献类型：
--
作者：
Sanders KM;Koh SD;Ro S;Ward SM
胃肠运动是由消化道的肌层--肌层的协调收缩引起的。在胃肠道的大部分部位，平滑的肌肉被组织成两层环状或纵向取向的肌束。平滑肌细胞在细胞之间形成电连接和机械连接，以促进收缩的协调。钙离子通过质膜上的离子通道进入细胞内，引起细胞内钙离子浓度的升高，从而发生兴奋-收缩偶联。Ca~(2+)与钙调蛋白结合激活肌球蛋白轻链激酶，随后肌球蛋白的磷酸化启动跨桥循环。肌球蛋白磷酸酶使肌球蛋白去磷酸化以放松肌肉，而一个被称为钙敏化的过程调节磷酸酶的活性。胃肠道平滑肌肉是“自主的”，并产生不依赖神经输入的自发电活动(慢波)。固有的起搏器活动来自Cajal间质细胞，这些间质细胞与平滑肌细胞电耦合。胃肠道肌肉收缩活动的模式由支配平滑肌细胞和间质细胞的肠运动神经元的输入决定。在这里，我们提供了一个细胞和机制的概述，产生平滑肌收缩行为和胃肠道运动。
Gastrointestinal motility results from coordinated contractions of the tunica muscularis, the muscular layers of the alimentary canal. Throughout most of the gastrointestinal tract, smooth muscles are organized into two layers of circularly or longitudinally oriented muscle bundles. Smooth muscle cells form electrical and mechanical junctions between cells that facilitate coordination of contractions. Excitation–contraction coupling occurs by Ca2+ entry via ion channels in the plasma membrane, leading to a rise in intracellular Ca2+. Ca2+ binding to calmodulin activates myosin light chain kinase; subsequent phosphorylation of myosin initiates cross-bridge cycling. Myosin phosphatase dephosphorylates myosin to relax muscles, and a process known as Ca2+ sensitization regulates the activity of the phosphatase. Gastrointestinal smooth muscles are ‘autonomous’ and generate spontaneous electrical activity (slow waves) that does not depend upon input from nerves. Intrinsic pacemaker activity comes from interstitial cells of Cajal, which are electrically coupled to smooth muscle cells. Patterns of contractile activity in gastrointestinal muscles are determined by inputs from enteric motor neurons that innervate smooth muscle cells and interstitial cells. Here we provide an overview of the cells and mechanisms that generate smooth muscle contractile behaviour and gastrointestinal motility.