The endothelial glycocalyx affords compatibility of Starling's principle and high cardiac interstitial albumin levels

• Published in: Cardiovascular research 2007-02, Vol.73 (3), p.575-586
• Main Authors: JACOB, Matthias, BRUEGGER, Dirk, REHM, Markus, STOECKELHUBER, Mechthild, WELSCH, Ulrich, CONZEN, Peter, BECKER, Bernhard F
• Format: Article
• Language: English
• Subjects: Albumins - metabolism; Albumins - pharmacology; Animals; Biological and medical sciences; Biological Transport; Capillary Permeability; Cardiology. Vascular system; Coronary Disease - metabolism; Coronary Disease - pathology; Coronary heart disease; Coronary Vessels - ultrastructure; Edema - metabolism; Edema - pathology; Electrolytes - pharmacology; Endothelium, Vascular - metabolism; Endothelium, Vascular - ultrastructure; Extracellular Fluid - metabolism; Exudates and Transudates - metabolism; Glycocalyx - metabolism; Glycocalyx - ultrastructure; Guinea Pigs; Heart; Heparin Lyase; Immunohistochemistry; Medical sciences; Microscopy, Electron; Models, Animal; Perfusion; Pressure; Starch - pharmacology; Venules
• ISSN: 0008-6363; 1755-3245
• DOI: 10.1016/j.cardiores.2006.11.021

To test the role of an oncotic pressure gradient across the endothelial glycocalyx with respect to extravasation of fluid and colloids and development of tissue edema in a whole organ setting. We measured filtration in the intact coronary system of isolated guinea pig hearts, comparing colloid-free perfusion and perfusion with 1.67% albumin or 2% hydroxyethylstarch (oncotic pressures 5.30 vs. 11.10 mm Hg, respectively). Heparinase was used to alter the endothelial glycocalyx. Extremely high net organ hydraulic conductivity was obtained with colloid-free perfusion (9.14 microl/min/g tissue). Supplementing perfusate with albumin caused a significant decrease, also vs. hydroxyethylstarch (1.04 vs. 2.67 microl/min/g, p < 0.05). Albumin also lowered edema formation vs. the other perfusion modes (p < 0.05). Stripping the glycocalyx of heparan sulfate reduced the effect of colloids, especially that of albumin. The steady-state concentrations of hydroxyethylstarch and albumin in the mixed interstitial fluid leaving the intact coronary bed averaged about 95% of the intravascular level. Electron and light microscopy indicated that colloid extravasated mainly in the venular sections. We propose a low-filtration model for the coronary system with different barrier properties in arteriolar/capillary and venular sections. Arteriolar/capillary: very little fluid and colloid extravasation due to the endothelial surface layer formed by the glycocalyx and albumin plus the endothelial strand barrier; venular: little net extravsation of fluid and colloids despite large pores, because of low hydrostatic and oncotic pressure differences between intra- and extravascular spaces. The latter sites provide physiological access of large solutes (colloids) to the tissue.