title: Studies on contact activation: effects of surface and inhibitors.
abstract: Contact activation is initiated when the plasma proteins, Hageman factor (factor XII), prekallikrein and high molecular weight kininogen interact with negatively charged materials. The activation of the intrinsic pathway of blood coagulation and the production of bradykinin are among the sequelae of contact activation. The kinetics of the activation of the contact system are modified by plasma inhibitors, C1 inhibitor being quantitatively the most important. We propose that the activation of the system requires that the stimulus provided by the surface must be greater than a threshold value to overcome the effects of the inhibitors. We show in this paper that the amount of surface required for activation is much reduced in the absence of C1 inhibitor (Hereditary Angioedema) or in the cold where the inhibitor loses much of its effectiveness. Antithrombin III inhibition of activated Hageman factor is augmented by heparin which is also an activator of Hageman factor. The rate constants for inhibition remain much lower than for C1 inhibitor, however.
authors.affiliation: Department of Medicine, State University of New York, Stony Brook 11794-8161.
authors.forename: C L
authors.initials: CL
authors.lastname: Cameron
authors.forename: B
authors.initials: B
authors.lastname: Fisslthaler
authors.forename: A
authors.initials: A
authors.lastname: Sherman
authors.forename: S
authors.initials: S
authors.lastname: Reddigari
authors.forename: M
authors.initials: M
authors.lastname: Silverberg
mesh_terms: D000990:Antithrombin III / Q000494:pharmacology; D001777:Blood Coagulation; D001798:Blood Proteins / Q000378:metabolism*; D003174:Complement C1 Inactivator Proteins / Q000494:pharmacology; D005174:Factor XII / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007704:Kininogens / Q000378:metabolism; D011288:Prekallikrein / Q000378:metabolism; D013499:Surface Properties; D013696:Temperature
chemical_list: D001798:Blood Proteins; D003174:Complement C1 Inactivator Proteins; D007704:Kininogens; D000990:Antithrombin III; D005174:Factor XII; D006493:Heparin; D011288:Prekallikrein