FIGURE 2.

Models used for transport barrier and mechanosensor functions of the glycocalyx. (a) Flow through surface glycocalyx-junction break model of the endothelium.³¹ The resistance of the glycocalyx to water and solute flows is described using hydrodynamic models. Fiber diameters range from small (1–2 nm, representative of GAG side chains) to larger fibers (10 nm and adsorbed plasma proteins). Flows through the glycocalyx are funneled into infrequent breaks in the tight junction strands. Various combinations of fiber size and arrangement have been investigated which describe water and solute flows when the size and frequency of the breaks in the junction strand are measured (see text). (b) A specific form of the surface glycocalyx-junction break model based on the quasi periodic structures in Fig 1(d) and (e) is shown. The glycocalyx is modeled as branching clusters anchored to the peripheral actin band in the endothelial cell. The structures form the primary molecular filter on the luminal side of the intercellular junctions. When the fibers extend about 150 nm from the surface and breaks in the junction stand, up to 400 nm long and 20 nm wide, are present every 2–4 microns, the model describes the permeability properties of rat venular microvessels⁸⁷. Shear stress on the edge of these clusters transmits displacements to their anchoring sites in the endothelial actin cytoskeleton of the order of 10 nm. (a) Reprinted with permission from Elsevier and (b) Copyright 2003 National Academy of Sciences, USA, used with permission.