Rabbit Anti-Human PAI1 monoclonal antibody for WB. PAI (plasminogen activator inhibitor) belongs to serine protease inhibitor superfamily, and is the principal inhibitor of tissue-type and urokinase-type plasminogen activators (tPA and uPA). Platelets are the main source of the circulating PAI-1, but it is synthesized and secreted by many tissue and cell types, including fibroblasts, smooth muscle cells, endothelial cells, hepatocytes, and inflammatory cells. Expression of PAI-1 can be regulated at the transcriptional level by many factors including growth factors, cytokines, hormones, inflammatory factors, glucose or lipid metabolites, vascular tone regulating factors, chemicals, and other environmental or physical factors.