Somlyo A P, Devine C E, Somlyo A V, North S R
J Cell Biol. 1971 Dec;51(3):722-41. doi: 10.1083/jcb.51.3.722.
The contractile response of turtle oviduct smooth muscle to acetylcholine after 30 min of incubation of muscles in Ca-free, 4 mM ethylene (bis) oxyethylenenitrilotetraacetic acid (EGTA) solutions at room temperature was greater than the contractile response after 30 min of incubation in the Ca-free medium at 37 degrees C. Incubation in Ca-free solution at 37 degrees C before stimulation with acetylcholine in Ca-free solutions at room temperature also reduced the contractile response, suggesting that activator calcium was lost from the fibers at a faster rate at higher temperatures. Electron micrographs of turtle oviduct smooth muscle revealed a sarcoplasmic reticulum (SR) occupying approximately 4% of the nucleus- and mitochondria-free cell volume. Incubation of oviduct smooth muscle with ferritin confirmed that the predominantly longitudinally oriented structures described as the SR did not communicate with the extracellular space. The SR formed fenestrations about the surface vesicles, and formed close contacts (couplings) with the surface membrane and surface vesicles in oviduct and vena caval smooth muscle; it is suggested that these are sites of electromechanical coupling. Calculation of the calcium requirements for smooth muscle contraction suggest that the amount of SR observed in the oviduct smooth muscle could supply the activator calcium for the contractions observed in Ca-free solutions. Incubation of oviduct smooth muscle in hypertonic solutions increased the electron opacity of the fibers. A new feature of some of the surface vesicles observed in oviduct, vena caval, and aortic smooth muscle was the presence of approximately 10 nm striations running approximately parallel to the openings of the vesicles to the extracellular space. Thick, thin, and intermediate filaments were observed in turtle oviduct smooth muscle, although the number of thick filaments seen in the present study appeared less than that previously found in mammalian smooth muscles.
将龟输卵管平滑肌在室温下于无钙、4 mM 乙二醇双（氧乙基）次氮基四乙酸（EGTA）溶液中孵育30分钟后对乙酰胆碱的收缩反应，大于在37℃的无钙培养基中孵育30分钟后的收缩反应。在室温下于无钙溶液中用乙酰胆碱刺激之前，先在37℃的无钙溶液中孵育也会降低收缩反应，这表明在较高温度下，激活钙从纤维中流失的速度更快。龟输卵管平滑肌的电子显微镜照片显示，肌浆网（SR）占据了无细胞核和线粒体的细胞体积的约4%。用铁蛋白孵育输卵管平滑肌证实，被描述为SR的主要纵向排列结构不与细胞外空间相通。SR在表面囊泡周围形成窗孔，并在输卵管和腔静脉平滑肌中与表面膜和表面囊泡形成紧密接触（耦合）；有人认为这些是机电耦合的部位。对平滑肌收缩所需钙的计算表明，在输卵管平滑肌中观察到的SR量可以为在无钙溶液中观察到的收缩提供激活钙。在高渗溶液中孵育输卵管平滑肌会增加纤维的电子不透明度。在输卵管、腔静脉和主动脉平滑肌中观察到的一些表面囊泡的一个新特征是，存在大约10 nm的条纹，这些条纹大致平行于囊泡通向细胞外空间的开口。在龟输卵管平滑肌中观察到了粗、细和中间丝，尽管在本研究中看到的粗丝数量似乎比以前在哺乳动物平滑肌中发现的要少。
