CALCIUM DEPENDENCE OF MYOSIN PHOSPHORYLATION AND AIRWAY SMOOTH-MUSCLE CONTRACTION AND RELAXATION
CALCIUM DEPENDENCE OF MYOSIN PHOSPHORYLATION AND AIRWAY SMOOTH-MUSCLE CONTRACTION AND RELAXATION
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DOI：
10.1152/ajpcell.1986.250.4.c597
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发表时间：
1986-04-01
影响因子：
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通讯作者：
GERTHOFFER, WT
中科院分区：
文献类型：
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作者：
GERTHOFFER, WT
研究了犬气管平滑肌收缩舒张过程中肌球蛋白磷酸化和等张缩短速度的时间过程及稳态钙依赖性。肌球蛋白的去磷酸化与激动剂洗脱后快速松弛时等张缩短速度的衰减一致。然而，在无Ca2+生理盐溶液（PSS）诱导的缓慢弛豫过程中，缩短速度的衰减先于去磷酸化。等长应力发育和肌球蛋白磷酸化的甲胆碱剂量-反应曲线重叠，但在缩短速度剂量-反应曲线的左侧移位。肌球蛋白磷酸化的稳态Ca2+依赖性被定义为使用碳醇和K+作为激动剂。在细胞外CaCl2浓度逐步降低后，出现了明显的去磷酸化解离和松弛。这一结果与毒蕈碱激活有关，因为阿托品在K+刺激的肌肉中减少了松弛和去磷酸化的解离。肌球蛋白磷酸化与肌肉收缩完全分离，当肌肉在无Ca2+的PSS中受到碳二醇刺激时，再接受CaCl2收缩。除了肌球蛋白磷酸化外，机制似乎还调节气道肌张力和缩短速度，并讨论了两种可能性。
The time course and the steady-state calcium dependence of myosin phosphorylation and isotonic shortening velocity were studied during contraction and relaxation of canine tracheal smooth muscle. Dephosphorylation of myosin coincided with the decay of isotonic shortening velocity during rapid relaxation following agonist washout. However, the decay of shortening velocity preceded dephosphorylation during a slow relaxation induced by Ca2+-free physiological salt solution (PSS). Carbachol dose-response curves for isometric stress development and myosin phosphorylation were superimposable but shifted to the left of the shortening velocity dose-response. The steady-state Ca2+ dependence of myosin phosphorylation was defined using carbachol and K+ as agonists. There was a significant dissociation of dephosphorylation and relaxation following a stepwise reduction of extracellular CaCl2 concentration. This result was related to muscarinic activation because the dissociation of relaxation and dephosphorylation was reduced by atropine in muscles stimulated with K+. Myosin phosphorylation was completely dissociated from contraction when muscles were stimulated with carbachol in Ca2+-free PSS and contracted by readmission of CaCl2. Mechanisms in addition to myosin phosphorylation appear to regulate airway muscle tone and shortening velocity, and two possibilities are discussed.