Activation of Human Factor VII in Plasma and in Purified Systems
Activation of Human Factor VII in Plasma and in Purified Systems ROLES OF ACTIVATED FACTOR IX, KALLIKREIN, AND ACTIVATED FACTOR XII URI SELIGSOHN, BJARNE OSTERUD, STEPHEN F. BROWN, JOHN H. GRIFFIN, and SAMUEL I. RAPAPORT, Department of Medicine, University of California, San Diego 92093; and San Diego Veterans Administration Hospital, San Diego, California, and Department of Immunopathologjy, Scripps Clinic and Research Foundation, La Jolla, Californiia 92093 A B S T R A C T Factor VII can be activated, to a had no additional indirect activating effect in the molecule giving shorter clotting times with tissue fac- presence of plasma. These results demonstrate that tor, by incubating plasma with kaolin or by clotting both Factor XIIa and Factor IXa directly activate human plasma. The mechanisms of activation differ. With Factor VII, whereas kallikrein, through generation of kaolin, activated Factor XII (XIIa) was the apparent Factor XIIa and Factor IXa, functions as an indirect principal activator. Thus, Factor VII was not activated activator of Factor VII. in Factor XII-deficient plasma, was partially activated in prekallikrein and high-molecular weight kininogen INTRODUCTION (HMW kininogen)-deficient plasmas, but was activated in other deficient plasmas. After clotting, activated Factor VII activity, as measured in one-stage Factor Factor IX (IXa) was the apparent principal activator. VII clotting assays (1), increases several fold when Thus, Factor VII was not activated in Factor XII-, blood is exposed to a surface such as glass or kaolin (1), HMW kininogen-, XI-, and IX-deficient plasmas, but or when blood is allowed to clot (2). Factor VII activity was activated in Factor VIII-, X-, and V-deficient also increases when plasma from women taking oral plasmas.
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