Takagi T, Fukuoka H, Tan E C, Itoh N, Hotta K
Neurol Med Chir (Tokyo). 1989 Jul;29(7):557-62. doi: 10.2176/nmc.29.557.
Understanding of the pathogenesis of cerebral vasospasm requires basic study of the contraction mechanism of cerebral arteries. In this study, the morphological and biochemical properties of actomyosin from bovine cerebral arteries were examined. Arrays of thick and thin filaments were clearly seen on electron micrographs of a cross section of a muscle strip stretched to 1.5 times its normal length in Krebs-Ringer solution. The diameters of the thick and thin filaments were 110.0 +/- 19.9 A and 51.0 +/- 8.0 A, respectively. The average ratio of thick to thin filaments was about 1:15 to 1:16. The gel pattern of Ca2+-sensitive actomyosin extracted from bovine cerebral arteries revealed the presence of myosin, actin, and tropomyosin, but not skeletal troponin. The Mg-ATPase activity of actomyosin was greatly enhanced in the presence of Ca2+. Rapid superprecipitation occurred after the clearing phase, when 1 mM Mg-ATP was added to a suspension of actomyosin with 10(-5) M Ca2+. This superprecipitation did not occur with a lower Ca2+ concentration of 10(-8) M. Intracellular free Ca2+ appears to play a crucial role in the regulation of contraction and relaxation of cerebral arterial smooth muscle.
对脑血管痉挛发病机制的理解需要对脑动脉收缩机制进行基础研究。在本研究中，检测了牛脑动脉中肌动球蛋白的形态和生化特性。在克雷布斯-林格溶液中，将肌肉条拉伸至正常长度的1.5倍后，其横切面的电子显微照片上清晰可见粗细肌丝束。粗肌丝和细肌丝的直径分别为110.0±19.9埃和51.0±8.0埃。粗肌丝与细肌丝的平均比例约为1:15至1:16。从牛脑动脉中提取的钙敏感肌动球蛋白的凝胶图谱显示存在肌球蛋白、肌动蛋白和原肌球蛋白，但不存在骨骼肌肌钙蛋白。在钙离子存在的情况下，肌动球蛋白的镁-ATP酶活性大大增强。当向含有10(-5)M钙离子的肌动球蛋白悬浮液中加入1mM镁-ATP后，在澄清期后会迅速发生超沉淀。在较低的钙离子浓度10(-8)M时不会发生这种超沉淀。细胞内游离钙离子似乎在脑动脉平滑肌收缩和舒张的调节中起关键作用。
