UROKINASE LOCALIZATION AND ACTIVITY IN ISOLATED EOSINOPHILS

Urokinase-type plasminogen activator is implicated in cell invasion an d migration, In this study, we provide evidence for the presence of ur okinase-type plasminogen activator (3.5 +/- 1.5 ng/mg of cell protein) in isolated peripheral blood eosinophils, in comparison to 6.7 +/- 2. 3 ng/mg of protein in neutrophils, Both immunocytochemical and immunog old staining of urokinase-type plasminogen activator on electron micro scopy showed its localization in granules of resting cells, Mild stimu lation by platelet-activating factor induced a translocation of urokin ase-type plasminogen activator from the granules to the cell membrane and a formation of urokinase-type plasminogen activator capping, sugge sting a role for urokinase-type plasminogen activator in eosinophil mi gration, The activation of eosinophils led to the release of factor(s) which, after activation of pro-urokinase-type plasminogen activator, induced an inactivation of generated urokinase-type plasminogen activa tor, Our results suggest that urokinase-type plasminogen activator is implicated in activated eosinophils invasiveness because the exposure of urokinase-type plasminogen activator is regulated both in space and time. (C) 1998 Elsevier Science Ltd.