Interaction of Plasma Contact Activation Factors with Vascular Endothelium

Exposure of plasma to certain negatively charged substances initiates the intrinsic coagulation pathway and bradykinin formation (Kaplan and Silverberg, 1987). The three plasma proteins required for this surface-mediated process are Factor XII (also known as Hageman factor), high molecular weight kininogen (HK) and prekallikrein. Factor XII is a monomeric beta-globulin with a MW of 80 kD and circulates in normal plasma at a concentration of 30-35 μg/ml (Cochrane and Wuepper, 1971) (Table 1). It is capable of undergoing autoactivation to the serine protease FXIIa (Silverberg, Dunn et al., 1980a; Wiggins and Cochrane, 1979) and this autoactivation is initiated by polyanionic substances such as glass, kaolin, and dextran sulfate. Known natural activators include certain mucopolysaccharides or proteoglycans (Hojima, Cochrane et al., 1984; Silverberg and Diehl, 1987), sulfatides (Shimada, Sugo et al., 1985), phospholipids (Schousboe, 1990), endotoxin (Morrison and Cochrane, 19741, and urate crystals (Ginsberg,...