Ghitescu L, Galis Z, Simionescu M, Simionescu N
Institute of Cellular Biology and Pathology, Bucharest, Romania.
J Submicrosc Cytol Pathol. 1988 Oct;20(4):657-69.
The interaction of exogenous albumin with the continuous endothelium of large vessels and microvessels of various organs was investigated in situ in mouse. Bovine serum albumin either tagged with 5 nm gold particles (Alb-Au) or radioiodinated was perfused for 3 to 30 min. The following tissues were processed for electron microscopy: heart (coronaries and microvessels), aorta, vena cava, diaphragm (phrenic arteries, arterioles, capillaries, venules, phrenic veins), and brain cortex. Morphometric analysis showed that in all organs examined, except brain, endothelium of capillaries and postcapillary venules possesses specific binding sites for Alb-Au virtually restricted to plasmalemmal vesicles. The latter contain 1,000 times more particles than the equivalent volume of the perfusate. The Alb-Au binding is saturable and competed by monomeric albumin. Commonly, in these capillary endothelia, coated pits and coated vesicles did not bind Alb-Au. Starting with 3 min and especially at longer time points, tracer-labeled vesicles apparently discharged the ligand into the subendothelial space. At variance, in the endothelium of arteries, arterioles, muscular venules, and veins, usually few vesicles were labeled by rare particles in concentration comparable with that of the perfused tracer. In these endothelia, vesicle Alb-Au content did not increase with time and was not influenced by competition with monomeric albumin. Same differences in albumin uptake between successive vascular segments were found by light microscopy autoradiography with monomeric radioiodinated albumin perfused for 3 or 30 min. The results suggest that among vessels with continuous endothelium, albumin binds and is intensely transported in the capillaries and postcapillary venules of the diaphragm and heart. The rest of the examined vessels perform a nonspecific, low rate uptake, possibly in fluid phase.
在小鼠体内原位研究了外源性白蛋白与各种器官大血管和微血管连续内皮的相互作用。用5纳米金颗粒标记的牛血清白蛋白（Alb-Au）或放射性碘化的牛血清白蛋白灌注3至30分钟。对以下组织进行电子显微镜处理：心脏（冠状动脉和微血管）、主动脉、腔静脉、膈肌（膈动脉、小动脉、毛细血管、小静脉、膈静脉）和大脑皮层。形态计量分析表明，在所有检查的器官中，除了大脑，毛细血管和毛细血管后微静脉的内皮具有Alb-Au的特异性结合位点，实际上仅限于质膜小泡。后者所含颗粒比等量灌注液多1000倍。Alb-Au结合是可饱和的，并被单体白蛋白竞争。通常，在这些毛细血管内皮中，有被小窝和有被小泡不结合Alb-Au。从3分钟开始，尤其是在更长的时间点，示踪剂标记的小泡显然将配体释放到内皮下间隙。不同的是，在动脉、小动脉、肌性小静脉和静脉的内皮中，通常很少有小泡被浓度与灌注示踪剂相当的稀有颗粒标记。在这些内皮中，小泡Alb-Au含量不随时间增加，也不受单体白蛋白竞争的影响。用放射性碘化单体白蛋白灌注3或30分钟，通过光学显微镜放射自显影在连续血管段之间也发现了白蛋白摄取的相同差异。结果表明，在具有连续内皮的血管中，白蛋白在膈肌和心脏的毛细血管和毛细血管后微静脉中结合并被强烈转运。其余检查的血管进行非特异性的低速率摄取，可能是在液相中摄取。
