Effect of coumadin‐induced coagulopoietin plasma on vitamin K‐dependent carboxylation of liver microsomes

Summary. Coumadin‐treated rabbits have a humoral substance(s) (coagulopoietin) which is capable of elevating vitamin K‐dependent coagulation factors when injected into recipient rabbits (Karpatkin & Karpatkin, 1973). Biologic levels of coagulation factors II, V, VII and X; immunologic levels of factors II and X; and vitamin K‐dependent liver microsomal carboxylase activity were measured in recipient rabbits receiving coumadin‐induced coagulopoietin plasma. Factor II biologic activity increased 3·5‐fold compared to the increase in immunologic activity. Factor X biologic activity increased 1·7‐fold compared to the increase in immunologic activity. This indicates an increase in specific activity of factors II and X. Coumadin‐induced coagulopoietin plasma had no effect on vitamin K‐dependent liver microsomal carboxylase activity in vitro. However, livers obtained from recipient animals treated with coumadin‐induced coagulopoietin plasma enhanced their carboxylase activity (compared to control animals) 2·4‐fold employing endogenous microsomal precursor for carboxylation, and 6·2‐fold employing synthetic substrate, phe‐leu‐glu‐glu‐val. Thus, coumadin‐induced coagulopoietin plasma enhances the biologic activity of vitamin K‐dependent coagulation factors II, VII, and X as well as the ex vivo vitamin K‐dependent carboxylase activity of liver microsomes.