title: The primary plasminogen-activator inhibitors in endothelial cells, platelets, serum, and plasma are immunologically related.
abstract: Monospecific antiserum to an unusually stable Mr 50,000 plasminogen-activator inhibitor (PAI) purified from cultured bovine aortic endothelial cells was employed in conjunction with reverse fibrin autography to determine whether human platelets, serum, and plasma contain immunologically related inhibitors. Reverse fibrin autography revealed the presence of a Mr 50,000 inhibitor in the platelet and serum samples but not in normal plasma. However, a Mr 50,000 inhibitor was detected in plasma obtained from individuals with increased PAI activity. In each case, treatment of the sample with the anti-inhibitor serum removed the Mr 50,000 inhibitor. The inhibitor present in each sample neutralized exogenously added tissue-type plasminogen activator in a rapid manner. Inhibition was associated with the formation of a NaDodSO4-resistant enzyme-inhibitor complex of Mr 120,000. Again, treatment of the samples with the anti-inhibitor serum removed both the inhibitory activity and the component in these samples that binds to tissue-type plasminogen activator. Thus, the rapidly acting PAI present in human platelets, serum, and patient plasma is immunologically related to the PAI synthesized by cultured bovine aortic endothelial cells. This molecule may be the physiologically relevant inhibitor of plasminogen activator in the vascular system and, as such, may serve an important role in regulating the initiation of vascular fibrinolysis.
mesh_terms: D001792:Blood Platelets / Q000201:enzymology / Q000276:immunology; D003429:Cross Reactions; D004727:Endothelium / Q000201:enzymology / Q000276:immunology; D006801:Humans; D046911:Macromolecular Substances; D008970:Molecular Weight; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors*; D015849:Plasminogen Inactivators; D011480:Protease Inhibitors / Q000097:blood* / Q000276:immunology; D011485:Protein Binding; D010959:Tissue Plasminogen Activator / Q000037:antagonists & inhibitors
chemical_list: D046911:Macromolecular Substances; D015849:Plasminogen Inactivators; D011480:Protease Inhibitors; D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator