Inhibition of the Platelet Function by the Effect of Plasmin on Human Factor VIII

Plasmin-treated human purified factor VIII prepared from normal and afibrinogenemia plasmas inhibits the ADP-induced aggregation and the collagen-induced 14C serotonin release of normal and von Willebrand human platelet rich plasmas (PRP). These results reconfirm the fact that the inhibition of the human platelet function by the effect of plasmin on the plasmatic protein is mainly linked to the digested factor VIII but not to the fibrinogen,fact that we had previously proved when ADP-induced aggregation of normal washed platelets was inhibited by plasmin-treated normal human serum,but not by plasmin-treated von Willebrand plasma. The factor VIII breakdown products were revealed by crossed immunoelectrophoresis,sepharose 4B chromatography and SDS Polyacrylamide electrophoresis.

The defective ADP-induced aggregation that we have observed in PRP from patients between the 8th and the 24th hour of thrombolithic treatment,is only due to the proteolithic effect of plasmin on the plasmatic factor VIII and not to a direct action of the plasmin on the platelet membrane,since washed platelets from these patients aggregate normally by ADP with normal platelet poor plasma(PPP),and the collagen-induced 14C serotonin release is also correct.