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 molecules can modify the platelet surface charge and thus its electrophoretic mobility. Electrophoretic quasi elastic light scattering (ELS) is a technique that permits the rapid and accurate determination of electrophoretic mobility of platelets. ELS was used to study changes in the platelet electrophoretic mobility induced by platelet activation and by fibrinogen binding. The platelet electrophoretic mobility decreases from -2 (mu-cm)/(V-s) to -0.5 (mu-cm)/(V-s) when the platelet is activated with either 1 microM ADP, 10 microM epinephrine or 0.5 NIH U/ml alpha-thrombin. Aspirin inhibits the ADP induced platelet activation and surface charge reduction. Thrombin overcomes the aspirin inhibition indication that the platelet surface charge reduction is associated with platelet activation. The magnitude of the decrease in the platelet electrophoretic mobility varies with the platelet donor and the extent of platelet activation. Platelet activation enhances the fibrinogen induced surface charge reduction, which is consistent with fibrinogen binding. Thus, ELS is shown to be a sensitive means to directly assess platelet activation and ligand binding.