Bradykinin and alpha-thrombin increase human umbilical vein endothelial macromolecular permeability by different mechanisms

Bradykinin and alpha-thrombin both increase endothelial macromolecular perm eability, however the mechanism for this effect is unclear. Human umbilical vein endothelial cell (HUVEC) permeability to human serum albumin was incr eased by 1 mu M alpha-thrombin (AT) or bradykinin (BK), but the kinetics of the permeability response were different. Intracellular calcium mobilizati on of HUVEC by AT was increased, yet BK had no effect on intracellular calc ium. Distribution of F-actin and content was increased by AT as early as 10 minutes after administration, yet BK had no affect on F-actin when compare d to control. We hypothesized that BK may increase HUVEC permeability by pr oducing matrix metalloproteinase-2 (MMP-2). The AT-treated HUVEC produced a n intermediate 64 kDa MMP-2, whereas BK-treated HUVEC increased the interme diate 64 kDa MMP-2 and also an active 62 kDa MMP-2. Pre-treatment of the HU VEC with tissue inhibitor of matrix metalloproteinase-2 slightly decreased the AT-induced increase in macromolecular permeability and completely inhib ited the BK-induced increase in macromolecular permeability.