van Deurs B, Röpke C, Westergaard E
Cell Tissue Res. 1976 May 26;168(4):507-25. doi: 10.1007/BF00216000.
The microvasculature of lymph nodes and Peyer's patches consists of arterioles, capillaries and venules. The postcapillary segment comprises high-endothelial venules (HE venules) as well as ordinary venules. In order to study the ultrastructure of the microvasculature, particularly with respect to the nature of intercellular junctions, lanthanum and ruthenium red were used as tracers. Furthermore, to evaluate the permeability properties of the different segments of the microvasculature, intravenously injected horseradish peroxidase (HRP; MW: 40,000) was used. All segments of the microvasculature are permeable to HRP. However, the mechanism of transport across the vascular wall varies in the different segments, apparently correlated with a gradual decrease in number of transport vesicles and a gradual attenuation in the sealing of the endothelial cells. Tight junctions are present in arterioles, and it is assumed that HRP reach the basal lamina exclusively by vesicular transport. Incomplete or focal tight junctions are present in the capillaries, and both intercellular and vesicular pathways are observed. In the venules the intercellular pathway seems to be the dominant one, while vesicular transfer is negligible. However, some micropinocytic vesicles in the HE venule endothelial cells probably represent the initial stage of an intracellular digestion.
淋巴结和派尔集合淋巴结的微脉管系统由小动脉、毛细血管和小静脉组成。毛细血管后段包括高内皮微静脉（HE微静脉）以及普通微静脉。为了研究微脉管系统的超微结构，特别是细胞间连接的性质，使用镧和钌红作为示踪剂。此外，为了评估微脉管系统不同节段的通透性，使用静脉注射辣根过氧化物酶（HRP；分子量：40,000）。微脉管系统的所有节段对HRP均具有通透性。然而，HRP穿过血管壁的机制在不同节段有所不同，这显然与转运小泡数量的逐渐减少以及内皮细胞封闭性的逐渐减弱有关。小动脉中存在紧密连接，推测HRP仅通过小泡转运到达基膜。毛细血管中存在不完全或局灶性紧密连接，观察到细胞间和小泡途径。在微静脉中，细胞间途径似乎是主要途径，而小泡转运可忽略不计。然而，HE微静脉内皮细胞中的一些微吞饮小泡可能代表细胞内消化的初始阶段。
