The mechanism of excitation-contraction coupling in phenylephrine-stimulated human saphenous vein
The mechanism of excitation-contraction coupling in phenylephrine-stimulated human saphenous vein
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DOI：
10.1152/ajpheart.01129.2001
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发表时间：
2002-10-01
影响因子：
4.8
通讯作者：
Van Breemen, C
中科院分区：
文献类型：
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作者：
Crowley, CM;Lee, CH;Van Breemen, C
人大隐静脉(HSV)是冠状动脉血运重建术中应用最广泛的移植物，在围手术期易发生痉挛。本研究的目的是阐明激动剂引起血管兴奋-收缩偶联的机制(S)。在苯肾上腺素(PE；50微米)激活过程中，利用共聚焦显微镜对未扩张的完整HSV节段进行等长收缩实验和细胞内钙离子浓度([Ca~(2+)](I))成像。用PE刺激会产生持续收缩。预先用5um硝苯地平或50um SKF-96365(电压和受体共同作用的钙通道阻断剂)可使肌电产生减少25%-30%。Ca~(2+)成像显示PE仅引起短暂的[Ca~(2+)](I)升高，提示Ca~(2+)只起很小的作用。然而，当在无钙介质中不能维持PE收缩时，则需要基础钙水平。根据瞬时的钙离子反应，似乎钙离子以外的信号必须维持PE引起的紧张性收缩，例如那些使肌丝对钙敏感的信号。在收缩的高峰期应用HA-1077(一种Rho激酶抑制剂)完全取消了反应的平台期，而应用金雀异黄素(一种酪氨酸酶抑制剂)使这一阶段减少了大约50%。上述结果表明，虽然瞬时的钙信号有助于力量的发展，但HSV中PE收缩的平台期的维持是Rho激酶和酪氨酸磷酸化使肌丝Ca~(2+)敏化的结果。阐明单纯疱疹病毒兴奋-收缩偶联的机制可能有助于制定缓解移植静脉痉挛的治疗策略。
The human saphenous vein (HSV) is the most widely used graft in coronary artery revascularization procedures and is susceptible to spasm perioperatively. The aim of this study is to elucidate the mechanism(s) of agonist-induced excitation-contraction coupling in this vessel. Isometric contraction experiments were combined with in situ smooth muscle intracellular Ca2+ concentration ([Ca2+](i)) imaging by confocal microscopy of intact undistended HSV segments during activation with phenylephrine (PE; 50 muM). Stimulation with PE produced a sustained contraction. Pre-incubation with 5 muM nifedipine, a blocker of the L-type voltage-operated Ca2+ channel, or 50 muM SKF-96365, a blocker of both the voltage- and receptor-operated channels, reduced force generation by 25-30%. Ca2+ imaging revealed that PE elicited only a transient rise in [Ca2+](i), suggesting that Ca2+ plays only a minor role. However, a requirement for basal Ca2+ levels was demonstrated when PE contractions could not be maintained in Ca2+-free medium. In light of the transient Ca2+ response, it appears that signals other than Ca2+ must maintain the tonic contraction elicited by PE, such as those that sensitize the myofilaments to Ca2+. Application of HA-1077 (a Rho kinase inhibitor) at the peak of the contraction completely abolished the plateau phase of the response, whereas application of genistein (a tyrosine kinase inhibitor) reduced this phase by similar to50%. The foregoing results suggest that, whereas the transient Ca2+ signal can contribute to the development of force, maintenance of the plateau phase of the PE contraction in the HSV is the result of myofilament Ca2+ sensitization by Rho kinase and tyrosine phosphorylation. The elucidation of the mechanisms of excitation-contraction coupling in the HSV may be useful for the development of therapeutic strategies for the alleviation of vein graft spasm.