ELECTROPHORETIC LIGHT-SCATTERING-STUDIES ON THE INTERACTION OF FIBRINOGEN WITH RESTING AND ACTIVATED HUMAN PLATELETS

The interaction of the platelet surface with agonist or adhesive molec ules can modify the platelet surface charge and thus its electrophoret ic mobility. Electrophoretic quasi elastic light scattering (ELS) is a technique that permits the rapid and accurate determination of electr ophoretic mobility of platelets. ELS was used to study changes in the platelet electrophoretic mobility induced by platelet activation and b y fibrinogen binding. The platelet electrophoretic mobility decreases from - 2 (mu-cm)/(V-s) to - 0.5 (mu-cm)/(V-s) when the platelet is act ivated with either 1 muM ADP, 10 muM epinephrine or 0.5 NIH U/ml alpha -thrombin. Aspirin inhibits the ADP induced platelet activation and su rface charge reduction. Thrombin overcomes the aspirin inhibition indi cation that the platelet surface charge reduction is associated with p latelet activation. The magnitude of the decrease in the platelet elec trophoretic mobility varies with the platelet donor and the extent of platelet activation. Platelet activation enhances the fibrinogen induc ed surface charge reduction, which is consistent with fibrinogen bindi ng. Thus, ELS is shown to be a sensitive means to directly assess plat elet activation and ligand binding.