Vascular glycocalyx sodium store – determinant of salt sensitivity?

Abstract

Smart mechanisms allow frictionless slipping of rather rigid erythrocytes (red blood cells, RBC) through narrow blood vessels. Nature solved this problem in an elegant way coating the moving object (RBC) and the tunnel wall (endothelium) by negative charges (glycocalyx). As long as these surfaces are intact, repulsive forces create a 'security zone' that keeps the respective surfaces separated from each other. However, damage of either one of these surfaces causes loss of negative charges, allowing an unfavorable physical interaction between the RBC and the endothelium. It has been recently shown that any alteration of the endothelial glycocalyx leaves nasty footprints on the RBC glycocalyx. In this scenario, sodium ions hold a prominent role. Plasma sodium is stored in the glycocalyx partially neutralizing the negative surface charges. A 'good' glycocalyx has a high sodium store capacity but still maintains sufficient surface negativity at normal plasma sodium. A 'bad' glycocalyx shows the opposite. This concept was used for the development of the so-called 'salt blood test' (SBT) that quantitatively measures RBC sodium store capacity of the glycocalyx and thus indirectly evaluates the quality of the inner vessel wall. In an initial step, the applicability of the SBT was tested in eight different medical facilities. The study shows that an increased salt sensitivity, as measured by the SBT, is more frequently found in individuals with a hypertensive history, despite antihypertensive medication. Taken together, preservation of the endothelial glycocalyx appears to be of utmost importance for maintaining a well-balanced function of the vascular system.