Purified human factor VIII procoagulant protein: comparative hemostatic response after infusions into hemophilic and von Willebrand disease dogs.

Abstract

The procoagulant protein F.VIII:C is noncovalently bound to von Willebrand factor (vWF) to give the factor VIII macromolecular complex. New highly purified preparations of isolated human F.VIII:C, devoid of vWF and about 500,000-fold purified, were administered to hemophilia A and von Willebrand disease (vWD) dogs to determine their hemostatic effectiveness and survival in the circulation. Two preparations of F.VIII:C were used: peak 1, with active components of Mr 185,000-280,000, and peak 2, with a single component of Mr 170,000. In hemophilic dogs, with no plasma F.VIII:C but normal vWF, both preparations immediately elevated plasma F.VIII:C to expected levels, promptly stopped induced and spontaneous hemorrhages, and gave sustained plasma levels of F.VIII:C. The isolated F.VIII:C immediately complexed with endogenous vWF in hemophilic plasma and was eliminated exponentially, with a half-life (t1/2) of about 9 hr. Survival of peak 2 F.VIII:C was longer than that of peak 1 material. In contrast, F.VIII:C complexed to vWF in a therapeutic concentrate administered to hemophilic dogs was eliminated biexponentially with first-phase t1/2 of 3.2 hr and second-phase t1/2 of 9 hr. In vWD dogs with no vWF and reduced F.VIII:C levels, the isolated F.VIII:C produced supernormal levels of F.VIII:C without effect on induced bleeding. It was rapidly eliminated from plasma with a t1/2 of about 1 hr, as was the complexed F.VIII:C in the concentrate. These data indicate that isolated F.VIII:C promptly complexes with vWF and in this form is highly effective in controlling hemophilic hemorrhages with good survival in plasma. Without endogenous vWF with which to complex, the F.VIII:C is promptly eliminated.

Effect of Synthetic Colloid Administration on Coagulation in Healthy Dogs and Dogs with Systemic Inflammation

“…This is consistent with findings from studies in humans documenting mild acquired von Willebrand disease after administration of rapidly degradable low MW HES such as tetrastarch, with activities returning to normal 5 hours after administration 10. Decreased FVIII activity occurs in dogs with von Willebrand disease because of the stabilizing role of vWF on circulating FVIII levels;26 therefore, one would expect decreased FVIII activity would be seen in conjunction with the decreased vWFAg and vWFCBA. Conversely, two human studies reveal that tetrastarch doses up to 50–70 mL/kg IV were administered without changes in FVIII concentration 27, 28.…”

Effect of recombinant factor VIIa on the hemostatic defect in dogs with hemophilia A, hemophilia B, and von Willebrand disease.

“…The secondary BT was performed by shaving off the clot at the primary site to restart bleeding. In hemophilic subjects, the secondary BT is >15 min; in normal animals, it is <5 min (22). The design of the experiments was to test the effect of rF.VIIa in two ways: (i) infusion before the secondary BT was done-i.e., prevention of prolonged bleeding and (ii) infusion while the nail was actively bleeding-i.e., stanching of bleeding in progress.…”

Native multimer analysis of plasma and platelet von Willebrand factor compared to denaturing separation: Implication for the interpretation of satellite bands

“…von Willebrand factor (vWF) is a large, adhesive, multimeric glycoprotein, which supports platelet adhesion and aggregation to the sub-endothelium in primary hemostasis [1], and stabilizes factor VIII during secondary hemostasis by acting as a carrier and protector for factor VIII [2]. The protein circulates in human plasma at concentrations of between 8 and 25 mg/mL [3] as a series of heterogeneous multimers ranging in size from about 500 kDa to over 20 000 kDa [4].…”