ASSEMBLY OF THE HUMAN PLASMA KININ-FORMING CASCADE ALONG THE SURFACE OF VASCULAR ENDOTHELIAL-CELLS

The generation of bradykinin by contact activation requires autoactiva tion of factor XII (Hageman factor) upon initiating surfaces, conversi on of prekallikrein to kallikrein, and digestion of high-molecular-wei ght (HMW) kininogen. Endothelial cells have a high-affinity receptor t hat binds either HMW kininogen or factor XII in a zinc-dependent inter action, and activation of factor XII can occur along this surface to i nitiate kinin formation. Tissue injury, exposure of proteoglycans, or release of mast cell heparin will markedly accelerate these reactions. The bradykinin released binds to endothelial cell B-2 receptors along the inner surface of blood vessels which results in dilatation and in creased vascular permeability.