Humoral factor that specifically regulates prothrombin (factor II) levels (coagulopoietin-II)

Prothrombin (Factor II) was decreased in rabbits by injection of a goat antiserum to prothrombin. When plasma from these rabbits was injected into normal animals, circulating prothrombin increased in the recipients, suggesting transfer of a humoral regulating factor ("coagulopoietin-II"). This coagulopoietin-II resisted boiling for 20 min. On Sephadex G-50 gel filtration, it remained in the retained volume, suggesting a molecular weight of less than 30,000. In an in vitro liver system, prothrombin increased in the incubation medium in the presence of coagulopoietin-II.