Zn²⁺- and uPA-induced adhesion of U937 cells: effect of inhibitors. (A) Adhesion of U937 cells on VN-coated wells in response to 50 μmol/L Zn²⁺ (○) or 50 nmol/L uPA (•) was performed in the absence or presence of various concentrations of 1-10-phenanthroline. Basal adhesion in the absence of uPA or Zn²⁺ was 0.05 to 0.1 units of absorbance. Data represent the mean ± SEM (n = 3) of a typical experiment. Similar results were obtained in three separate experiments. (B) The adhesion of U937 cells in response to 50 nmol/L uPA (filled symbols) or 50 μmol/L Zn²⁺ (open symbols) was performed for 2 hours. Thereafter, 100 nmol/L PAI-1 (circles) or 500 μmol/L 1-10-phenanthroline (squares) was added for different time intervals as indicated, and residual adherent cells were quantitated. Data represent the mean ± SEM (n = 3) of a typical experiment. Similar results were obtained in three separate experiments.