Studies on isolated smooth muscle cells: The contractile apparatus.
Studies on isolated smooth muscle cells: The contractile apparatus.
复制标题
对分离的平滑肌细胞的研究：收缩装置。
作者：
J. Small
平滑肌细胞可以从豚鼠的结肠带肌中分离，当用Triton X-100（0-05%）处理使其具有渗透性时，其显示出对Ca的敏感性，从而用MgATP收缩。收缩率约为10 μ m s-1，与完整肌肉缩短的最大速度密切相关。这种部分去膜的肌细胞的电子显微镜显示，约16纳米直径的肌球蛋白丝存在于僵硬和放松状态。此外，肌动蛋白和肌球蛋白丝通常以组的形式存在，其大小与光镜下僵直细胞中可识别的原纤维大致相当。致密体和10-nm的细丝被发现位于肌动蛋白-肌球蛋白细丝组之间。粗肌球蛋白丝可以通过在松弛条件下使细胞破碎而分离。这些天然肌丝的长度范围可达约8微米，并显示出与来自纯化平滑肌肌球蛋白的肌丝相同的结构组织：在肌丝末端没有中心裸露区和裸露边缘，约0-2微米长。缺乏双极性的天然平滑肌肌球蛋白丝和缺乏，在收缩装置中，肌动蛋白相关的结构相当于Z线表明，剪切量，可以发生在肌动蛋白和肌球蛋白丝之间是相当大的比骨骼肌。
Smooth muscle cells may be isolated from the taenia coli muscle of the guinea pig which, when made permeable by treatment with Triton X-100 (0-05%) show a sensitivity to Ca for contraction with MgATP. The rate of contraction, about 10 micron s-1, corresponds closely to the maximum velocity of shortening of the intact muscle. Electron microscopy of such partially demembranated muscle cells shows that myosin filaments of about 16-nm diameter are present in both the rigor and the relaxes states. In addition, the actin and myosin filaments are commonly seen to be associated in groups corresponding approximately in size to the fibrils recognizable in cells in rigor in the light microscope. The dense bodies and the 10-nm filaments are found located between the actin-myosin filament groups. The thick myosin filaments may be isolated by fragmentation of the cells under relaxing conditions. These native filaments range up to about 8 micron in length and show the same structural organization as filaments aseembled from purified smooth muscle myosin: there is no central bare zone and bare edges, about 0-2 micrin long, occur at the filament ends. The lack of bipolarity of the native smooth muscle muosin filaments and the absence, in the contractile apparatus, of actin-associated structures equivalent to Z-lines suggests that the amount of shearing that can occur between the actin and myosin filaments is considerably greater than in skeletal muscle.