An assay for plasminogen activator inhibitor in human platelets is described. With this assay we find an average value of 6.8 × 10−8 IU/platelet (S.D. = 3.0 × 10−8; n = 20) in a healthy population. We characterized the PA-inhibitor from platelets and identified it as endothelial cell type plasminogen activator inhibitor, by its immunologic and functional properties. Besides the plasma pool of plasminogen activator inhibitor with a very high turnover rate, platelets constitute a second pool of plasminogen activator inhibitor in the circulation of the same order of magnitude. The two different pools of plasminogen activator inhibitor might have a different physiologic function.
Keywords
Fibrinolysis - Platelets - Plasminogen activator inhibitor Summary