The human complement system in thrombin-mediated platelet function.
Thrombin-mediated platelet membrane-specific uptake of C3 and C5 was demonstrated by radiolabeled components and was visualized electron microscopically utilizing a ferritin marker conjugated to monospecific antibody to each component. The role of complement in thrombin-induced platelet function was determined. Though complement was not essential for thrombin-induced platelet aggregation and release of serotonin, these activities were significantly increased if complement was present. The release of serotonin was found to be a nonlytic process because under the conditions employed, no lactic dehydrogenase was released. The activation of complement was induced by a mechanism which has not been previously described. Thrombin associated with the platelet membrane presumably formed a C3 convertase that entered the known complement sequence at the C3 stage and proceeded to activate the terminal components through the known sequence to C9.
D001792:Blood Platelets / Q000502:physiology* / Q000648:ultrastructure; D003176:Complement C3 / Q000378:metabolism; D003182:Complement C5 / Q000378:metabolism; D003165:Complement System Proteins / Q000502:physiology*; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D010974:Platelet Aggregation; D012701:Serotonin / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology / Q000502:physiology*
D003176:Complement C3; D003182:Complement C5; D012701:Serotonin; D003165:Complement System Proteins; D007770:L-Lactate Dehydrogenase; D013917:Thrombin