Fig. 3. Induction of actin polymerization by excess PL in resting platelets. Actin filament content in different platelets extracts was determined by the Dnase 1 inhibition assay as indicated in Materials and Methods. Ctrl, the actin filament content in resting platelets; PC 2min and PC 30min, the actin filament content in platelets incubated with (0.2)PC for 2 and 30 minutes, respectively; PS 2min and PS 30min, the actin filament content in platelets incubated with (0.2)PS for 2 and 30 minutes, respectively; Calp⁺A23, the actin filament content in platelets pre-treated with 100 µg/ml calpeptin for 30 minutes and then activated with the calcium ionophore A23187 (1 µM). Black and hatched bars represent the actin filament content in the absence or presence of 50 µM cytochalasin D (CD), respectively. The data are expressed as the mean of eight individual experiments ± s.d.