Rembold C M, Murphy R A
Department of Physiology, University of Virginia School of Medicine, Charlottesville 22908.
Circ Res. 1988 Sep;63(3):593-603. doi: 10.1161/01.res.63.3.593.
Our objective was to test the hypotheses that 1) myoplasmic [Ca2+] is the primary determinant of crossbridge phosphorylation and that 2) phosphorylation is the primary determinant of crossbridge interactions with the thin filament in swine carotid arterial smooth muscle. We tested these hypotheses by evaluating the relation between aequorin-estimated myoplasmic [Ca2+], myosin light chain phosphorylation, shortening velocity at zero load (V0), and stress at various times after stimulation with histamine, phenylephrine, and depolarization with KCl. Agonist-induced changes in myoplasmic [Ca2+] were associated with predictable changes in myosin phosphorylation. Depolarization required proportionally higher changes in myoplasmic [Ca2+] for a given change in myosin phosphorylation. The relation between phosphorylation and V0 or steady-state stress was invariant with all tested stimuli. This suggests that Ca2+-dependent crossbridge phosphorylation is the primary determinant of the mechanical response.
1）肌浆[Ca2+]是横桥磷酸化的主要决定因素，以及2）磷酸化是猪颈动脉平滑肌中横桥与细肌丝相互作用的主要决定因素。我们通过评估在用组胺、去氧肾上腺素刺激以及用氯化钾进行去极化后不同时间点，水母发光蛋白估计的肌浆[Ca2+]、肌球蛋白轻链磷酸化、零负荷缩短速度（V0）和张力之间的关系，来检验这些假设。激动剂诱导的肌浆[Ca2+]变化与肌球蛋白磷酸化的可预测变化相关。对于给定的肌球蛋白磷酸化变化，去极化需要成比例更高的肌浆[Ca2+]变化。磷酸化与V0或稳态张力之间的关系在所有测试刺激下均不变。这表明Ca2+依赖性横桥磷酸化是机械反应的主要决定因素。
