Predescu S A, Predescu D N, Palade G E
Division of Cellular and Molecular Medicine, University of California, San Diego 92122-0651, USA.
Am J Physiol. 1997 Feb;272(2 Pt 2):H937-49. doi: 10.1152/ajpheart.1997.272.2.H937.
We investigated the location and the structural identity of the small pore system, postulated by the pore theory of capillary permeability, using a murine heart perfusion system and small protein molecules as preferential probes for the small pores. Dinitrophenylated proteins were perfused in situ in the absence and in the presence of N-ethylmaleimide (NEM), a reagent known to interfere with membrane fusion of vesicular carriers with their target membranes. The exit pathways of the tracers from vascular lumina to the interstitia were followed by immunoelectron microscopy and by tissue fractionation biochemistry to quantitate their transport and to estimate the extent of transport inhibition by NEM. After 5 min of perfusion, all tracers used were found essentially restricted to plasmalemmal vesicles (PVs) within the endothelium and NEM inhibited their transport by 80-85%. The transport of [14C]inulin and [14C]sucrose, assumed to follow the paracellular pathway, was marginally affected by NEM. These findings indicate that PVs function as structural equivalents of the small pore system for molecules >2 nm in diameter.
我们使用小鼠心脏灌注系统，并以小蛋白质分子作为小孔的优先探针，研究了毛细血管通透性孔理论所假定的小孔系统的位置和结构特性。在不存在和存在N - 乙基马来酰亚胺（NEM）的情况下，将二硝基苯基化蛋白质原位灌注，NEM是一种已知会干扰囊泡载体与其靶膜的膜融合的试剂。通过免疫电子显微镜和组织分级生物化学追踪示踪剂从血管腔到间质的排出途径，以定量它们的转运并估计NEM对转运的抑制程度。灌注5分钟后，发现所有使用的示踪剂基本上都局限于内皮细胞内的质膜小泡（PVs），并且NEM抑制它们的转运达80 - 85%。假定遵循细胞旁途径的[14C]菊粉和[14C]蔗糖的转运仅受到NEM的轻微影响。这些发现表明，对于直径大于2 nm的分子，PVs起着小孔系统的结构等效物的作用。
