Summary
The in vivo effects of oral anticoagulant therapy with 4–hydroxycoumarins on various
vitamin K–dependent enzyme systems in man were compared. In hepatic microsomes obtained
from donors who has been treated with 4–hydroxycoumarins for more than 6 months, the
vitamin K 2,3 epoxide reductase activity and the DTT–dependent vitamin K quinone reductase
activity were diminished to 35% and 20% of the corresponding normal values. In the
non–hepatic tissues, only a small decrease in vitamin K 2,3 epoxide reductase activity
could be demonstrated, while no differences were found in the vitamin K quinone reductase
activities. In none of the tissues a significant increase of non–carboxylated precursor
proteins was observed, whereas also vitamin K hydroquinone–dependent carboxylase activities
seemed to be unaffected by the anticoagulant treatment.
Keywords
Vitamin K - Coumarin derivatives - Anticoagulant therapy - Carboxylase - Gammacarboxyglutamic
acid