Williams S K, Greener D A, Solenski N J
J Cell Physiol. 1984 Aug;120(2):157-62. doi: 10.1002/jcp.1041200208.
The transport of proteins across continuous capillary endothelium is believed to be mediated by micropinocytic vesicles which shuttle molecules between the lumenal and abluminal plasma membrane. We have studied the ability of capillary endothelial cells isolated from rat epididymal fat to endocytose fluorescently labelled ovalbumin within micropinocytic vesicles. Net association of fluorescent ovalbumin with endothelial cells reaches an equilibrium after 40 minutes of incubation. This equilibrium is presumably due to a balance between endocytosis and subsequent exocytosis of this protein. Capillaries equilibrated with fluorescent ovalbumin exhibited rapid exocytosis of this protein when it was removed from the external medium. The rate of endocytosis was concentration dependent and obeyed the kinetics expected for adsorptive phase endocytosis. High concentrations of ovalbumin stimulated the ingestion of 14C-sucrose, a marker of fluid endocytosis, suggesting that protein can affect the movement of vesicles within the endothelial cytoplasm. These results imply that capillary endothelium isolated from rat epididymal fat exhibits the ability to endocytose and subsequently exocytose protein. This demonstrates that the two components of endothelial vesicular transport or transcytosis can be observed and studied in a system of isolated capillary endothelium.
蛋白质通过连续毛细血管内皮的转运被认为是由微胞饮小泡介导的，这些小泡在管腔和管腔外质膜之间穿梭分子。我们研究了从大鼠附睾脂肪中分离的毛细血管内皮细胞在微胞饮小泡内对荧光标记卵清蛋白进行内吞的能力。荧光卵清蛋白与内皮细胞的净结合在孵育40分钟后达到平衡。这种平衡可能是由于该蛋白质的内吞作用和随后的胞吐作用之间的平衡。用荧光卵清蛋白平衡的毛细血管在从外部培养基中去除该蛋白质时表现出该蛋白质的快速胞吐作用。内吞速率是浓度依赖性的，并且符合吸附相内吞作用预期的动力学。高浓度的卵清蛋白刺激了14C-蔗糖的摄取，14C-蔗糖是液体内吞作用的标志物，这表明蛋白质可以影响内皮细胞质内小泡的运动。这些结果表明，从大鼠附睾脂肪中分离的毛细血管内皮具有内吞并随后胞吐蛋白质的能力。这证明在内皮小泡转运或转胞吞作用的两个组成部分可以在分离的毛细血管内皮系统中被观察和研究。
