Electron microscopic changes in blood platelets induced by bacterial lipopolysaccharide

Abstract

Degranulation and destruction of platelet limiting membranes were observed in blood platelets incubated with bacterial lipopolysaccharide. The earliest changes seemed to be both lysis of platelets, with dissolution of the limiting membrane, and loss of platelet contents with preservation of the limiting membrane. These alterations in ultrastructure began soon after addition of lipopolysaccharide. Individual platelets in aggregates characteristically were separated by discrete masses of osmiophilic material, approximately 300 A in diameter. Similar masses were seen in platelet aggregates in vivo but were not observed when platelets were incubated with lipopolysaccharide in a plasma-poor medium. After 2 hr incubation with lipopolysaccharide some platelets were observed to have undergone little change in morphology, compared with control samples. The destructive changes were largely prevented by incubation at 4°C, or by the presence of citrate. Although fibrin was not observed in proximity to platelet aggregates formed in vivo, material resembling fibrin was seen in association with cellular debris in large vessels.