Proteins released by platelets following thrombin activation. (A) The proteins from the supernatant of nonactivated (C) and thrombin-activated platelets (A) were solubilized in SDS reducing buffer, separated by one-dimensional SDS-PAGE (4%-20% gradient gel) and stained with colloidal Coomassie blue. (B) A duplicate of the gel was probed with a monoclonal antibody to thrombospondin (clone p10). Molecular weight markers are indicated.