title: Factor VIII lability, protein C and other vitamin K-dependent proteins.
abstract: The stability of factor VIII was studied in plasmas from patients on long-term warfarin therapy. The percent residual factor VIII activity (F.VIII:C) after incubation at 37 degrees C for 4 hr was higher in warfarinized patients than in normal subjects; 76.9 +/- 10.8% (mean +/- SD) of the initial F.VIII:C in the patients versus 61.6 +/- 5.8% in normal subjects (p less than 0.001). On the whole, neither protein C nor vitamin K-dependent coagulation factors except factor VII activity (F.VII:C) correlated with the residual F.VIII:C. There was a negative and weak correlation between the residual F.VIII:C at 4 hr and either the initial F.VIII:C or F.VII:C. Another experiment using protein C depleted plasma showed a relatively enhanced stability of F.VIII:C in the protein C deficiency. These results indicate that factor VIII is more stable in warfarinized plasma, and that protein C and vitamin K-dependent coagulation factors are not the sole, main factor responsible for such a phenomenon.
mesh_terms: D001779:Blood Coagulation Factors / Q000032:analysis; D002318:Cardiovascular Diseases / Q000097:blood / Q000188:drug therapy; D004355:Drug Stability; D005169:Factor VIII / Q000378:metabolism*; D006023:Glycoproteins / Q000032:analysis*; D006801:Humans; D011486:Protein C; D011516:Prothrombin / Q000032:analysis; D012016:Reference Values; D014812:Vitamin K / Q000097:blood*; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D001779:Blood Coagulation Factors; D006023:Glycoproteins; D011486:Protein C; D014812:Vitamin K; D014859:Warfarin; D011516:Prothrombin; D005169:Factor VIII