Mechanism of controlling blood-cell passage between the sinus endothelial cells

采用冷冻断裂、氚提取和镧示踪技术观察大鼠窦内皮细胞紧密连接的精细结构。在冻裂复制品中，经常在窦内皮细胞的基底外侧表面观察到紧密连接的分节链和凹槽。部分股线或凹槽不连续，未闭合。在硝酸镧处理的窦性内皮细胞纵切面上，大多数位于相邻内皮细胞外侧表面的基底部。除连接膜融合外，相邻内皮细胞的细胞间隙是电子密集的，硝酸镧的浸润不受这些紧密连接的干扰。利用硝酸镧透射电镜证实了窦内内皮细胞表面连通小管系统（SCCS）的存在，并通过计算机辅助重建证实了小管的三维排列。窦内皮细胞的SCCS由细长的小管组成，小管呈分支状，与质膜吻合，呈连续性。计算机辅助重建发现，从质膜的不同部位内陷的小管彼此相连，并穿透窦内皮细胞，在细胞质中形成复杂的网络。用激光共聚焦扫描和电子显微镜观察了小窝蛋白-3在鼻窦内皮细胞中的免疫定位。在鼻窦内皮细胞的免疫荧光显微镜下，内皮细胞的轮廓用抗caveolin-3标记。内皮细胞胞质内的应力纤维附近有斑点状的小泡蛋白-3。超薄冷冻切片的免疫金电镜显示，窦内皮细胞的顶、侧、基质膜的小泡中有抗小泡蛋白-3标记，细胞质中有一些囊泡轮廓。少

The fine structure of the tight junctions between the rat sinus endothelial cells was examined using freeze-fracture, triton extraction, and lanthanum-tracer techniques. In freeze-fracture replicas, the segmented strands and grooves of the tight junctions were frequently observed on the basolateral surfaces of the sinus endothelial cells. Some strands or grooves were discontinuous and were not closed. In the vertical sections of the sinus endothelial cells treated with lanthanum nitrate, most of them were situated on the basal part of the lateral surfaces of the adjacent endothelial cells. The intercellular spaces of the adjacent endothelial cells except for the fusion of the junctional membranes, were electron dense and the infiltration of lanthanum nitrate was found not to be interrupted by these tight junctions.The existence of the surface connected canalicular system (SCCS) in the sinus endothelial cells has been demonstrated by transmission electron microscopy using lanthanum nitr … More ate and, the three dimensional arrangement of the canaliculi was also demonstrated by computer-aided reconstruction. The SCCS of the sinus endothelial cells consisted of slender canaliculi which were branched, anastomosed, and showed continuity with the plasma membrane. From a computer-aided reconstruction the canaliculi, which were invaginated from various sites of the plasma membrane, were found to be continuous with each other and penetrate the sinus endothelial cell, to form a complex network in the cytoplasm.The immunolocalization of caveolin-3 in the sinus endothelial cells was examined with confocal laser scanning and electron microscopes. In immunofluorescence microscopy of the sinus endothelial cells, the contours of the endothelial cells were labelled with anti-caveolin-3. Caveolin-3 was present near stress fibers in the cytoplasm of the endothelial cells in a speckled pattern. Immunogold electron microscopy of ultrathin cryosections revealed anti-caveolin-3 labeling in caveolae in the apical, lateral, and basal plasma membranes and some vesicular profiles in the cytoplasm of the sinus endothelial cells. Less