Development of increased factor VII activity during the spontaneous coagulation of blood

Granulocyte elastase cleaves human high molecular weight kininogen and destroys its clot-promoting activity

Purified human granulocyte elastase cleaved purified human high molecular weight (HMW) kininogen into multiple low molecular weight fragments, and destroyed the clot-promoting activity of the HMW kininogen. Elastase digestion did not release kinin or destroy the bradykinin portion of the HMW kininogen molecule; kallikrein could release kinin from the elastase-induced low molecular weight digestion products of HMW kininogen. Purified alpha 1-antitrypsin prevented the destruction of the clot-promoting activity of HMW kininogen by elastase; it also delayed the clotting of normal plasma. Elastase may play a significant role in altered hemostasis as well as fibrinolysis, in areas of inflammation to which polymorphonuclear leukocytes have been attracted.

Activation of human factor VII in plasma and in purified systems: roles of activated factor IX, kallikrein, and activated factor XII

Factor VII can be activated, to a molecule giving shorter clotting times with tissue factor, by incubating plasma with kaolin or by clotting plasma. The mechanisms of activation differ. With kaolin, activated Factor XII (XII(a)) was the apparent principal activator. Thus, Factor VII was not activated in Factor XII-deficient plasma, was partially activated in prekallikrein and high-molecular weight kininogen (HMW kininogen)-deficient plasmas, but was activated in other deficient plasmas. After clotting, activated Factor IX (IX(a)) was the apparent principal activator. Thus, Factor VII was not activated in Factor XII-,HMW kininogen-, XI-, and IX-deficient plasmas, but was activated in Factor VIII-, X-, and V-deficient plasmas. In further studies, purified small-fragment Factor XII(a) (beta-XII(a)), kallikrein, and Factor IX(a) were added to partially purified Factor VII and to plasma. High concentrations of beta-XII(a) activated Factor VII in a purified system; much lower concentrations of beta-XII(a) activated Factor VII in normal plasma but not in prekallikrein or HWM kininogen-deficient plasmas. Kallikrein alone failed to activate partially purified Factor VII but did so when purified Factor IX was added. Kallikrein also activated Factor VII in normal, Factor XII-, and Factor IX-deficient plasmas. Purified Factor IX(a) activated partially purified Factor VII and had no additional indirect activating effect in the presence of plasma. These results demonstrate that both Factor XII(a) and Factor IX(a) directly activate human Factor VII, whereas kallikrein, through generation of Factor XII(a) and Factor IX(a), functions as an indirect activator of Factor VII.