Rat coagulation factors V, VIII, XI, and XII: vitamin K dependent

When rats were given single or multiple doses of warfarin, the levels of prothrombin and factors VII, IX, and X were depressed, as expected. However, modest reductions of factors V, VIII, XI, and XII, but not of fibrinogen, also occurred. The levels of all eight factors promptly returned to normal when vitamin K1 was given. Warfarin-resistant rats had no depression of any of the eight factors. When vitamin K deficiency was induced by internal or external biliary fistula, factors II-VII-IX-X decreased sharply and factors V-VIII-XI-XII decreased modestly. Again, all depression were promptly reversed by vitamin K1. Isolated livers from warfarinized rats did not generate the classic vitamin K-dependent factors during 5 h of perfusion but did generate small amounts of factors V, XI, and XII, although less than normal. The isolated rat liver apparently does not generate factor VIII.