Comparison of platelet aggregability and P-selectin surface expression on platelets isolated by different methods

Three methods commonly used for isolation of blood platelets from plasma we re compared. Platelets were isolated by: 1) a washing method; 2) a method o f metrizamide-gradient centrifugation; 3) a modified method of gel-filtrati on. The last method employed BSA-Sepharose gel instead of routinely used Se pharose gel saturated with BSA. BSA-Sepharose gel was prepared by covalent binding of thermally deactivated BSA to CNBr-activated Sepharose 2B. In con trast to platelets isolated by the other methods, an aggregability of the g el-filtered platelets and control platelets in plasma, both activated with ADP, were comparable. When expression of P-selectin on the surface of fresh ly isolated platelets was examined, the gel-filtered platelets exhibited th e same extent of fluorescence signal as platelets in the citrated blood, wh ereas platelets isolated by the other methods exhibited twice the extent of the signal. The methods involving the centrifugation process cause a low b ut a significant platelet activation. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.