Inhibition of Human Platelet Aggregation by Plasmin Digests of Human and Bovine Fibrinogen Preparations: Role of Contaminating Factor VIII-related Material

Preparations of human fibrinogen, digested by plasmin, inhibited ADP-inducedplatelet aggregation; the inhibitory activity was confined to the small dialyzablefragments accumulating during the degradation. Purified large molecular weightfragments D and E had no effect on ADP-induced aggregation, but fragment E inhibited thrombin-induced aggregation.Extensively degraded bovine fibrinogenpreparations also inhibited platelet aggregation by ADP. Both human and bovinefibrinogen preparations were contaminated with factor VIII-related material(factor VIII-related antigen and factorVIII procoagulant activity, respectively);separation of factor VIII-related materialfrom human or bovine fibrinogen by gelchromatography and subsequent plasmindigestion of the fractions revealed thatthe inhibitory activity was mainly linkedto digested factor VIII-related material.This inhibitory activity was dialyzable.The effect of fibrinogen digests on plateletaggregation should therefore be reconsidered.

Submitted on May 4, 1973 Revised on January 17, 1974 Accepted on January 23, 1974