Activation studies on human platelets using electrophoretic and quasi-elastic light scattering

Our interest in human platelets is based on the pathological activity of platelets during formation of thrombi in connection with atherogenesis. The shape change is the first step of platelet activation and aggregation. Thus starting with the appearance of blebs and pseudopods a change in surface charge density and hydrodynamic radius of the cells in physiological solution occurs. These parameters and their changes can be measured by quasi-elastic light scattering. We also found that platelets slightly activated by mechanical stress recover when incubated at 37°C for about half an hour. Significant differences in the electrophoretic mobility as well as in the diffusion constant could be found when the sample was cooled down from 37°C to 20°C indicating shape change. These findings with laser light scattering dependent activation of platelets is not occurring continuously but there seems to be a critical temperature range for activation of human blood platelets of healthy donors. To see activation caused by addition of an agent, we observed dose-dependent change of electrophoretic mobility with thrombin.