Properties of antithrombin III depleted plasma I. Effect of heparin

Antithrombin III depleted plasma was prepared by immunosorption. The plasma was shown to retain all factors necessary for normal coagulation and the level of the protease inhibitors α 1-antitrypsin and α 2-macroglobulin was not affected. The addition of heparin to this plasma had no effect on the inhibition of thrombin and factor X a and only slightly prolonged the coagulation time as measured by the APTT test. When purified antithrombin III was added to the depleted plasma the effect of heparin on the inhibition of thrombin and factor X a and on the over-all clotting time was restored. The formation of antithrombin III-heparin complex in heparinized plasma was shown using an immunosorption technique.