EFFECTS OF BACTERIAL ENDOTOXIN ON RABBIT PLATELETS : II. ENHANCEMENT OF PLATELET FACTOR 3 ACTIVITY IN VITRO AND IN VIVO

Incubation of rabbit platelet-rich plasma with bacterial endotoxin results in activation of platelet factor 3, a precursor of blood thromboplastin. This platelet-endotoxin interaction is dose- and temperature-dependent, and is similar to the effects of antigen-antibody union in the presence of platelets. Injection of endotoxin intravenously is associated with a transient increase in platelet factor 3. Since platelet factor 3 can be demonstrated in platelet-poor plasma as well as platelet-rich plasma after endotoxin injection, it seems likely that an actual transfer of factor 3 from platelets to plasma occurs and that this activity is then rapidly inactivated or cleared from the blood stream.