ULTRASTRUCTURAL LOCALIZATION OF CONTRACTILE PROTEIN (THROMBOSTHENIN) IN HUMAN PLATELETS USING AN UNLABELED ANTIBODY-PEROXIDASE STAINING TECHNIQUE

Abstract

Soluble horseradish peroxidase-antihorseradish peroxidase (rabbit) complex was used to localize the actomyosin-like contractile protein, thrombosthenin, in both intact human platelets (Epon-embedded) and ultrathin sections (methacrylate-embedded). Antibody staining of ultrathin sections showed the presence of membrane-associated and cytoplasmic thrombosthenin. Antibody staining of intact cells showed that membrane-associated thrombosthenin was localized, at least in part, in the exterior, "fluffy" coat of the platelet. Even after prolonged fixation and/or incubation with the various antisera, we were unable to demonstrate antibody penetration of intact, fixed platelets. Brief treatment with Pronase removed the surface-localized proteinaceous material and completely abolished all antibody staining.