FLOW SENSING AT THE ENDOTHELIUM-BLOOD INTERFACE

Viscoelastic and polyelectrolytic heparan sulfate proteoglycan (syndec an) integrated into the membrane of vascular endothelial cells may ser ve as a flow sensor. This biosensor macromolecule responds to shear st ress by a conformational change. Cations function as a first messenger in the signal transduction chain for a dilatory vessel reaction with increasing blood flow. Application of Na-23(+) NMR techniques proved u seful in the characterization of shear stress-dependent conformational changes and reversible Na+ binding of proteoheparan sulfate, a strong ly negatively charged proteoglycan. Ca2+ ions interfere with Na+ uptak e and release in a competitive or cooperative manner. The adsorption o f heparan sulfate proteoglycan at hydrophobic silica surfaces, as meas ured by in situ ellipsometry, was shown to be dependent on both genera l electrostatic and cation-specific ion binding actions. The interfaci al behaviour of this macromolecule is characterized by an increase in the adsorbed amount upon addition of Ca2+, while Mg2+ induces the oppo site effect of much smaller magnitude. (C) 1998 Elsevier Science B.V.