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

脾窦内皮细胞被认为是控制血细胞通过脾索的关键部位，在超微结构上也与其他血管内皮细胞有很大不同。特别突出的是它们的形状和排列，就像一个桶的杆，在它们的基部纵向分布着一个高度有序的收缩应力纤维网络。此外，与丰富的小泡和应力纤维密切相关的管泡结构也很明显。细胞内游离Ca2+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/或机械应力也会引起Ca2+振荡。导致Ca2+振荡的确切机制尚不清楚，但已经提出了ip3受体敏感性的振荡变化，不同Ca2+池的调谐Ca2+释放，Ca2+通过非选择性Ca2+通道的节律性进入，细胞形态的变化以及内质Ca2+- atp酶的参与。考虑到窦内皮细胞内的应激分子是收缩的，窦内皮细胞内的小泡、Ca2+储存ER、IP3R和RyR可能参与了应激的收缩。纤维。此外，已经证实了RyR在内皮细胞中的存在及其对Ca2+振荡的贡献，但其在内皮细胞中的定位并不十分清楚。因此，采用激光共聚焦扫描和电镜观察大鼠脾窦内皮细胞内腔内溶酶和Ca2+储存ER的分布以及IP3R和RyR的定位。组织冷冻切片的免疫荧光显微镜显示，IP3R和RyR定位于窦内皮细胞的质下区和细胞质。用铁氰化锇选择性染色肌肉细胞内的肌浆网和横小管，电镜观察到电子密集的管泡结构与腔泡和质膜紧密相连。免疫金电镜显示，在窦内皮细胞质下区域的小管泡结构中存在IP3R和RyR。推测窦内皮细胞的IP3R和RyR参与了应力纤维的收缩。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