Summary
The interaction between heparin, histidine-rich glycoprotein and antithrombin III
was studied in purified systems. Histidine- rich glycoprotein binds heparin and thereby
interferes with its interaction with antithrombin III, resulting in neutralization
of the anticoagulant activity. This interaction occurs with clinical grade heparin
as well as with high affinity (for antithrombin III) heparin and with a high affinity
heparin fragment with Mr. 4,300.
Low affinity heparin competes with high affinity heparin for the binding to histidine-rich
glycoprotein which results in an apparent increase of the anticoagulant activity of
high affinity heparin.
The interaction between heparin and histidine-rich glycoprotein is counteracted by
Ca2+-binding anticoagulants, indicating that it is dependent on the presence of divalent
metal ions. Ethylenediaminetetraacetate is a much more potent inhibitor of the interaction
between heparin and histidine-rich glycoprotein than citrate.
Keywords
Heparin - Histidine-rich glycoprotein - Anticoagulant activity