Effect of protease inhibitors on tryptase-induced proliferative responses. BaF3/PAR-2 cells were plated as outlined in the legend to Fig 1 and incubated for 48 hours with 0.1 U/L (3 pmol/L) β-tryptase or β-tryptase that had been preincubated with specified protease inhibitors for 15 minutes at 37°C. Inhibitor concentrations were 2 mmol/L EDTA, 10 μg/mL soybean trypsin inhibitor (STI), 2 mmol/L benzamidine (BZA), and 0.2 mmol/L leupeptin. As shown, tryptase-mediated proliferative responses are specifically abrogated by protease inhibitors previously shown to block tryptase hydrolytic activity (see Table 2). Results represent the mean ± SEM of four wells from a single representative set of experiments.