title: Regulation of factor VIIa activity in plasma: evidence that antithrombin III is the sole plasma protease inhibitor of human factor VIIa.
abstract: The inhibition of human factor VIIa by antithrombin III and normal human plasma was studied in the presence and absence of heparin. In the absence of heparin, no apparent inhibition of factor VIIa was observed in either system. In the presence of heparin, factor VIIa activity was inhibited 50% by purified antithrombin III and plasma in 90 min and 75 min, respectively. No inhibition of factor VIIa was observed in heparinized plasma previously depleted of antithrombin III by immunoaffinity adsorption. Incubation of factor VIIa with antithrombin III-heparin or heparinized plasma resulted in the formation of a covalent complex with an apparent molecular weight of 100 kilodaltons. These data indicate that antithrombin III appears to be the sole plasma protease inhibitor of human factor VIIa, and the expression of its inhibitory activity against factor VIIa is absolutely dependent upon the presence of exogenous heparin.
mesh_terms: D000990:Antithrombin III / Q000378:metabolism / Q000494:pharmacology*; D005167:Factor VII / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015942:Factor VIIa; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D011480:Protease Inhibitors / Q000097:blood
chemical_list: D011480:Protease Inhibitors; D000990:Antithrombin III; D005167:Factor VII; D006493:Heparin; D015942:Factor VIIa