The antiheparin effect of alpha1-acid glycoprotein and platelet material, evaluated by the heparin thrombin clotting time.

The effect on the heparin thrombin clotting time (HTCT) of a so-called acute phase protein, alpha1-acid glycoprotein, was studied in test systems consisting of purified fibrinogen, antithrombin III, heparin and thrombin, and compared to the effect of platelet material (crude platelet factor 4). In these test systems a physiological concentration of alpha1-acid glycoprotein (1 g/l) inhibited heparin more effectively than did soluble platelet material from 200 X 10(9) platelets/l. The present observations suggest that alpha1-acid glycoprotein is of great significance for the so-called heparin tolerance, whereas platelet material proved less important.