Permeability of muscle capillaries to small heme-peptides. Evidence for the existence of patent transendothelial channels
Permeability of muscle capillaries to small heme-peptides. Evidence for the existence of patent transendothelial channels
复制标题
肌肉毛细血管对小血红素肽的渗透性。
作者：
N. Simionescu;M. Siminoescu;G. Palade
本文用两种直径约为20埃的血红素肽（血红素十一肽[H11 P]，mol wt约1900;血红素八肽[H8 P]，mol wt约1550）作为肌毛细血管（大鼠膈肌）的探针分子。他们被定位在原位的过氧化物酶反应，通过添加咪唑的孵育介质增强。血浆样品的色谱分析表明，在实验期间，HP主要作为单体循环，并通过醛固定剂与血浆蛋白结合，结合程度约为50%（H8 P）至约95%（H11 P）。两种示踪剂主要通过质膜囊泡穿过内皮，质膜囊泡在三个连续的可分辨阶段中从内皮的血液前端到组织前端逐渐被标记（通过反应产物）。在每个阶段结束时，标记的程度达到大于90%的相应囊泡群体。标记的囊泡表现为孤立的单元或链，形成穿过内皮的开放通道。这些通道的通畅性检查标本倾斜和图形分析的图像。没有证据表明，早期或优先标记的细胞间连接和空间的反应产物。得出的结论是，通道是毛细管壁的小孔的结构等效物的最可能的候选者，因为它们是连续的、充满水的通道，并且具有小于100 A的一个或多个狭窄。其频率仍有待今后的工作确定。
Two heme-peptides (HP) of about 20-A diameter (heme-undecapeptide [H11P], mol wt approximately 1900 and heme-octapeptide [H8P], mol wt approximately 1550), obtained by enzymic hydrolysis of cytochrome c, were sued as probe molecules in muscle capillaries (rat diaphragm). They were localized in situ by a perixidase reaction, enhanced by the addition of imidazole to the incubation medium. Chromatography of plasma samples showed that HPs circulate predominantly as monomers for the duration of the experiments and are bound by aldehyde fixatives to plasma proteins to the extent of approximately 50% (H8P) to approximately 95% (H11P). Both tracers cross the endothelium primarily via plasmalemmal vesicles which become progressively labeled (by reaction product) from the blood front to the tissue front of the endothelium, in three successive resolvable phases. By the end of each phase the extent of labeling reaches greater than 90% of the corresponding vesicle population. Labeled vesicles appear as either isolated units or chains which form patent channels across the endothelium. The patency of these channels was checked by specimen tilting and graphic analysis of their images. No evidence was found for early or preferential marking of the intercellular junctions and spaces by reaction product. It is concluded that the channels are the most likely candidate for structural equivalents of the small pores of the capillary wall since they are continuous, water-filled passages, and are provided with one or more strictures of less than 100 A. Their frequency remains to be established by future work.