Ultrastructural analysis of the mechanism of the contraction of splenic sinus endothelial cells

以往的研究表明，脾静脉窦内皮细胞是控制血细胞通过脾索的关键部位，而且在超微结构上与其他血管内皮细胞有很大的不同。特别突出的是它们的形状和排列，就像桶的横杆一样，在它们的底部有一个高度有序的收缩应力纤维网络，纵向延伸。此外，靠近丰富的小窝和应力纤维的管状泡状结构也很明显。细胞内游离钙浓度的升高在内皮血管功能的调节中起着至关重要的作用，此外，激动剂和/或机械应激也会引起钙振荡。导致钙振荡的确切机制尚不清楚，但ip3受体敏感性的振荡变化、不同钙池的时间分辨钙释放、钙离子通过非选择性钙…的节律性进入。已经提出了更多的钙通道、细胞形态的改变和内质钙-三磷酸腺苷酶的参与。考虑到窦内皮细胞的应激收缩，窦内皮细胞上储存钙离子的内质网、IP3R和RyR可能参与了应激的收缩。纤维。此外，RyR在内皮细胞中的存在及其在钙振荡中的作用已经被证明，但在内皮细胞中的定位还不是很清楚。为此，本研究采用激光共聚焦扫描和电子显微镜技术，对大鼠脾静脉窦内皮细胞的胞浆和胞浆内的胞浆和胞浆内的IP3R和RyR进行了定位观察。用铁氰化铯处理的组织切片，选择性地对肌细胞的肌浆网和横管进行染色，观察到电子致密的管泡状结构与腔隙和质膜紧密相连。免疫金电镜示IP3R和RyR表达于窦内皮细胞质膜下区的管泡结构中。推测窦内皮细胞中的IP3R和RyR参与了应力纤维的收缩。较少

Endothelial cells of the splenic sinus have been previously investigated as a critical site for controlling blood cell passage through the splenic cord, and they have also been shown to be ultrastructurally quite different from other vascular endothelial cells. Particularly prominent are their shape and arrangement, like the staves of a barrel, with a highly ordered network of contractile stress fibers running longitudinally in their basal part. in addition, tubulovesicular structures in close apposition to abundant caveolae and stress fibers are conspicuous. An elevation in intracellular free Ca2+ concentration plays a crucial role in the regulation of endothelial vascular functions and, furthermore, agonists and/or mechanical stress also evoke Ca2+ oscillations. The exact mechanisms contributing to Ca2+ oscillation are unknown, but oscillatory changes in IP3-receptor sensitivity, tune-resolved Ca2+ release from different Ca2+-pools, the rhythmic entry of Ca2+ through non-selective ca … More tion channels, changes in cellular morphology and the involvement of endoplasmic Ca2+-ATPases have been proposed. Considering that the stress **ers in sinus endothelial cells are contracted, caveolae, Ca2+storing ER, IP3R, and RyR in sinus endothelial cells may be involved in the constriction of stress. fibers. in addition, the presence and contribution to Ca2+-oscillations of RyR in endothelial cells have been shown, but the localization in endothelial cells is not quite clear. Therefore, the distribution of caveolac and Ca2+storing ER and the localization of IP3R and RyR in the sinus endothelial cells of the rat spleen were examined by confocal laser scanning and electron microscopy.Immunofluorescence microscopy of tissue cryosections revealed IP3R and RyR to be localized in the subplasmalemmal area and cytoplasm of sinus endothelial cells. By electron microscopy of tissue sections treated with osmium ferricyanide to selectively stain the sarcoplasmic reticulum and transverse tubules in muscle cells, electron-dense tubulovesicular structures were observed to be in close apposition to caveolac and the plasma membrane. Immunogold electron microscopy revealed IP3R and RyR to be present in the tubulovesicular structure in the subplasmalemmal area of sinus endothelial cells. It is speculated that IP3R and RyR in sinus endothelial cells is involved in the constriction of stress fibers. Less