BACKGROUND Ultrastructural investigations of the endothelial glycocalyx reveal a layer adjacent to the cell surface with a structure consistent with the primary ultrafilter of vascular walls. Theory predicts this layer can be no greater than 200-300 nm thick, a result to be reconciled with observations that red cells and large macromolecules are excluded from a region 1 micrometer or more from the cell membrane. OBJECTIVE To determine whether this apparent inconsistency might be accounted for by a model of steady state water and protein transport through a glycocalyx bi-layer formed by a porous outer layer in series with a more selective inner layer. METHODS Expressions for coupled water and albumin fluxes through the two layers were used to describe steady state ultra-filtration though the bi-layer model. RESULTS Albumin accumulates at the interface between the porous layer and the selective inner layer. The osmotic pressure of accumulated albumin significantly modifies the observed permeability properties of the microvessel wall by an effective unstirred layer effect. CONCLUSIONS The model places significant constraints on the outer layer permeability properties . The only outer layer properties that are consistent with measured steady state filtration rates and models of red cell flux through microvessels are an albumin permeability coefficient and hydraulic conductivity more than an order of magnitude larger than the those of the inner layer.

中文翻译：

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内皮糖萼：屏障功能与红细胞血流动力学：通过由多孔外层和更具选择性的膜相关性内层形成的双层形成的稳态超滤模型。

背景技术对内皮糖萼的超微结构研究显示出与细胞表面相邻的层具有与血管壁的初级超滤器一致的结构。理论上预测该层的厚度不超过200-300 nm，这一结果与观察结果相符，即从细胞膜1微米或更大的区域排除了红细胞和大分子。目的要确定这种明显的不一致是否可以通过稳态状态下的水和蛋白质通过糖萼双层（由多孔外层与选择性更高的内层串联而成）双层传输来解释。方法通过两层模型耦合的水和白蛋白通量的表达式用于描述稳态超滤。结果白蛋白积聚在多孔层和选择性内层之间的界面上。积聚的白蛋白的渗透压通过有效的非搅拌层效应显着改变了微血管壁的通透性。结论该模型对外层渗透率特性有明显的限制。与测得的稳态过滤速率和通过微血管的红细胞通量模型一致的唯一外层特性是白蛋白渗透系数和水力传导率比内层大一个数量级。积聚的白蛋白的渗透压通过有效的非搅拌层效应显着改变了微血管壁的通透性。结论该模型对外层渗透率特性有明显的限制。与测得的稳态过滤速率和通过微血管的红细胞通量模型一致的唯一外层性质是白蛋白渗透系数和水力传导率，其比内层大一个数量级。积聚的白蛋白的渗透压通过有效的非搅拌层效应显着改变了微血管壁的通透性。结论该模型对外层渗透率特性有明显的限制。与测得的稳态过滤速率和通过微血管的红细胞通量模型一致的唯一外层特性是白蛋白渗透系数和水力传导率比内层大一个数量级。