(A) Time-dependent effects of plasmin 0.043 CTA U/mL (♦), 0.14 CTA U/mL (▴), and 0.43 CTA U/mL (•) on cGMP formation by human monocytes (10⁷ cells/mL) compared with controls without plasmin (▾). (B) Concentration-dependent effect of plasmin on generation of cGMP by monocytes stimulated for 1 minute. Cell suspensions were prewarmed to 37°C for 6 minutes before addition of plasmin for the periods indicated. Results are the mean ± SEM of 4 experiments each.