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Science 11 April 1969:
Vol. 164. no. 3876, pp. 181 - 183
DOI: 10.1126/science.164.3876.181
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Articles

Vitamin K and Coumarin Anticoagulants: Dependence of Anticoagulant Effect on Inhibition of Vitamin K Transport

Julius Lowenthal 1 and Henry Birnbaum 1

1 Department of Pharmacology and Therapeutics, McGill University, Montreal 109, Quebec, Canada

Coumarin anticoagulants inhibit the release of plasma clotting factor VII by vitamin K in liver slices from vitamin K-deficient animals without inhibition of protein synthesis. When the ratio of vitamin K to coumarin anticoagulant is kept constant, but the concentrations are increased, the inhibition disappears. This suggests that the pharmacological action of coumarin anticoagulants depends on irreversible inhibition of normal vitamin K transport to its site of action. At higher concentrations of vitamin K the inhibition can be surmounted, because vitamin K can enter the cell by an alternate route that is not inhibited by coumarin anticoagulants.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)