A Protein C (PC) concentrate may be useful in treating patients with congenital or acquired Protein C deficiencies. A method for preparation of a human Protein C concentrate has been developed using a by-product of American Red Cross Factor IX production as the starting material (Menache et. al. Blood, 64, 1220). Levels of other vitamin K dependent proteins in the Protein C concentrate were measured and found to be <10 units per 100 units of PC, except for Protein S. The level of Protein S as judged by immunological assay was 30 u/100 u PC. Assay of the PC concentrate using chrcmogenic substrates revealed that levels of thrombin, Factor 3�a and Factor IXa were less than 0.006 u/mL. In addition, Antithrombin III and ax -macroglobulin were not detected. The vivo effects of Protein C concentrate and Protein C activated by thrombin have been tested in anesthetized rabbits. Thrombin was removed from the activated Protein C by ion-exchange chromatography; depletion was verified by S-2238 or by a clotting assay (< 0.006 u/mL). Rabbits were injected with Protein C concentrate (400 ug/kg) or activated Protein C 24 - 48 ug/Kg). The activated partial thromboplastin time (APTT), FactorV (FV) and Factor VIII (FVIII) levels were measured in samples collected over the next three hours. Infusion of PC concentrate elevated the level of PC to 150% of the preinfusion level within 30 min. It did not change the levels of FV, FVIII, fibrinogen or platelet count. In contrast, infusion of activated Protein C produced progressive prolongation of the APTT. Levels of FV and FVIII were decreased to 25% and 50% of preinfusion levels, respectivelv, three hours after the infusion. Fibrinogen and platelet levels were unchanged during that period. These data demonstrate that activated human Protein C concentrate induces an anticoagulant effect that can be readily measured in rabbits.
Human protein C concentrate in the treatment of hemolytic uremic syndrome
