A model of the electrochemical equilibrium configuration of the capillary glycocalyx

A electrochemical theory of the surface glycocalyx on capillary endothelial cells is presented which models the structure as a matrix of electrostatically charged macromolecules hydrated in an electrolytic Newtonian fluid. In equilibrium it is assumed that a state of electroneutrality exists such that positively charged ions in the fluid balance the fixed negative charges bound to the macromolecules of the glycocalyx. Disturbances arising from mechanical deformation, flow, and chemical and/or electric potentials are introduced as perturbations away from the electroneutral equilibrium environment. In the presence of charged fluorescent macromolecules injected into the capillary lumen, the model predicts that chemical and electric potentials would result in a flux of ions and macromolecules into the layer at size- and charge-dependent rates until a new electroneutral environment is achieved that is in equilibrium with the solution in the capillary lumen. Model predictions are compared with experimental results and used to estimate the fixed-charge density of tile solid-bound charges in the endothelial-cell glycocalyx and the state of tension in the solid matrix in the equilibrium configuration.