Regulation of smooth muscle contraction through remodeling of actin filaments

1)Phx-1对平滑肌收缩的抑制作用的机制为了阐明2-氨基-4，4 α-二氢-4 α-7-二甲基-3H-吩恶嗪-3-酮（Phx-1）对平滑肌制备物的舒张作用的机制，我们研究了Phx-1对来自豚鼠盲肠的完整和带皮（细胞膜可固定化）制备物的收缩的作用。在完整的制剂中，Phx-1浓度依赖性地抑制由乙酰胆碱（ACh）或高K+诱导的收缩，IC 50值估计约为100 pM。在细胞内钙库耗尽的制剂中观察到类似的Phx-1对力的抑制作用。然而，在细胞膜去极化的准备在细胞外钙的情况下，Phx-1对咖啡因或乙酰胆碱诱导的收缩几乎没有影响。在皮肤制备物中，Phx-1在浓度高于100 μM时抑制Ca^2+-诱导的收缩。这些结果表明，Phx-1似乎具有直接的生物学活性， ...更多信息 虽然Phx-1对Ca^2+内流的抑制作用更强，但对肌动蛋白丝组织的暂时作用更强。2）肌球蛋白II的有效抑制剂blebbistatin对收缩丝的重塑我们研究了肌球蛋白II的有效抑制剂blebistatin对β-七叶皂苷剥皮的盲肠带的机械和结构特性的影响。Blebbistatin抑制Ca^2+诱导的收缩，对Ca^2+敏感性的影响很小，30 mM Mg^2+诱导的，肌球蛋白磷酸化无关的，力的发展，Blebistatin也通过Ca^2+去除加速舒张。上述<50>blebbistatin效应的IC_（1）值接近25 μ M。本研究结果表明，blebbistain直接干预跨桥相互作用。此外，blebbistatin抑制肌动蛋白和肌球蛋白丝的组织。由于blebbistatin不直接结合肌动蛋白，中断肌球蛋白丝似乎调节肌动蛋白丝组织。少

1)Mechanism of the inhibitory effects of Phx-1 on the smooth muscle contraction To elucidate the mechanisms of relaxing effect of 2-amino-4,4 a-dihydro-4 a-7-dimethyl-3H-phenoxazine-3-one (Phx-1) on the smooth muscle preparations, we investigated effects of Phx-1 on the contraction of both intact and skinned (cell membrane peremeabilized) preparations from guinea pig tenia cecum. In intact preparations, Phx-1 concentration-dependently suppressed the contraction induced by either acetycholine(ACh) or high-K+ with the IC50 value estimated at around 100 pM. Similar inhibitory actions of Phx-1 on force were observed in intracellular Ca store depleted preparations. In the cell membrane depolarized preparations in the absence of extracellular Ca, however, Phx-1 had little effects on the caffeine-or ACh-induced contraction. In skinned preparations, Phx-1 suppressed the Ca^<2+->induced contraction at concentrations higher than 100 μM. These results suggest that Phx-1 seems to have direct inhib … More itory effect on the actin filaments organization, although inhibitory effect, of the Phx-1 on the Ca^<2+>-influx is much stronger.2)Contractile filaments remodeling by blebbistatin, a potent inhibitor of myosin II We studied the effects of blebbistatin, a potent inhibitor of myosin II on the mechanical and structural properties of beta escin skinned taenia cecum. Blebbistatin inhibited both Ca^<2+> induced contraction with only little effects on the Ca^<2+> sensitivity for the force, and 30 mM Mg^<2+> induced, myosin phosphorylation independent, force development, Also, blebbistatin accelerated relaxation by Ca^<2+> removal. IC_<50> values of the blebbistatin effects presented above were nearly 25 micro M. The present results suggested that blebbistain directly interfare cross-bridge interaction. Furthermore, blebbistatin inhibited organization of actin-and myosin-filaments. Since blebbistatin did not bind to actin directly, disruption of myosin filaments seemed to modulate actin filaments organization. Less