Abstract-Descarboxyprothrombin(PIVKA II) is a precursor of prothrombin without biological activity, and it increases with vitamin K deficiency.We studied the time course changes in liver and plasma levels of PIVKA II during the progress of vitamin K deficiency in rats. Good correlation was observed between liver PIVKA II and plasma PIVKA II and between liver or plasma PIVKA II and plasma prothrombin in experiments in which rats were fed a vitamin K-deficient diet. Feeding of a vitamin K-deficient diet or fasting caused marked increases in liver and plasma PIVKA II in male rats and a weaker response in female rats. Warfarin, a vitamin K antagonist, caused an abrupt increase in liver PIVKA II, but the increase in plasma PIVKA II was delayed about 3 hr. Plasma prothrombin decreased from about 30 min later. Factor VII decreased similarly to prothrombin, and changes in the prothrombin time and activated partial thromboplastin time were slower than the changes in these substances.Sex differences were not seen in these warfarin actions.These observations indicate that liver and plasma PIVKA II are sensitive markers of vitamin K deficiency in rats, and assay of PIVKA II can be useful for analyzing the action mechanism of drugs which influence blood coagulation.

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