Figure 3: Mechanism to maintain a high fibrinolytic potential on VECs and its modification by PAI-1. Secreted- and retained-tPA readily activates cell-bound plasminogen on VECs (lower right), which amplifies plasminogen accumulation to newly exposed C-terminal lysine by plasmin-dependent cleavage of cell surface proteins (upper right). PAI-1 suppresses these mechanisms by removing retained tPA from VECs by forming high molecular weight complex (left).