Fig. 4. PMA-induced activation of caspase-3 is dependent on ROCK activation, F-actin polymerization and myosin ATPase activity. TF-1 cells were treated with PMA in the absence or presence of different pharmacological inhibitors as indicated (ROCK inhibitor: Y27632, 20 µM; F-actin polymerization inhibitor: Latrunculin B (L.B), 0.5 µM; myosin ATPase inhibitor: BDM, 5 µM). After 8 hours, cells were harvested and analyzed for caspase-3 activity as described in the Materials and Methods. Results are expressed as the increase in 405 nm absorbance by subtracting the reading values from those obtained in cells without PMA treatment from four independent experiments.