Moreland S, Antes L M, McMullen D M, Sleph P G, Grover G J
Bristol-Myers Squibb Pharmaceutical Research Institute, Department of Pharmacology, Princeton, NJ 08543.
Pflugers Arch. 1990 Oct;417(2):180-4. doi: 10.1007/BF00370697.
Two regulatory systems are believed to control the contractile state of vascular smooth muscle in vitro. In one, crossbridges are phosphorylated by myosin light-chain (MLC) kinase; these phosphorylated crossbridges are believed to predominate during force development. In the other system, the crossbridges are unphosphorylated (latchbridges); the latchbridges are thought to prevail during force maintenance. The role of these systems in the control of vascular resistance in vivo is unknown. This study compared MLC phosphorylation with vascular tone in canine anterior tibial arteries in vitro and in situ. The arteries were frozen at various times before and during stimulation with norepinephrine. Under both conditions, the levels of MLC phosphorylation were low at rest and increased transiently during norepinephrine stimulation. This increase was associated with stress development in vitro and with an increase in vascular resistance in situ. Thus, the biochemical changes measured in arteries in situ parallel those measured in vitro suggesting that the in vitro models are appropriate and useful for studying the physiological function of blood vessels. To our knowledge, this is the first demonstration of changing levels of MLC phosphorylation in an artery in situ.
人们认为有两种调节系统可控制体外血管平滑肌的收缩状态。在一种系统中，肌球蛋白轻链（MLC）激酶使横桥磷酸化；这些磷酸化的横桥被认为在力量产生过程中占主导地位。在另一种系统中，横桥未被磷酸化（闩锁桥）；闩锁桥被认为在力量维持过程中占优势。这些系统在体内控制血管阻力方面的作用尚不清楚。本研究比较了犬胫前动脉在体外和原位时MLC磷酸化与血管张力的关系。在去甲肾上腺素刺激之前和期间的不同时间点将动脉冷冻。在两种情况下，MLC磷酸化水平在静息时较低，在去甲肾上腺素刺激期间短暂升高。这种升高与体外的应力产生以及原位血管阻力的增加有关。因此，原位动脉中测量到的生化变化与体外测量的变化相似，这表明体外模型对于研究血管的生理功能是合适且有用的。据我们所知，这是首次证明原位动脉中MLC磷酸化水平的变化。
