Fig. 4. Pertussis toxin selectively inhibits chemotactic-peptide- but not colchicine-induced development of polarity. Neutrophils were treated without or with 450 ng/ml pertussis toxin (Ptx) as described in Materials and Methods, followed by resuspension in Gey's medium and incubation without (control) or with 1 nM fNLPNTL (CP) or with 10 µM colchicine (colch.) for 30 minutes at 37°C. Cells were fixed with glutaraldehyde and the percentage of spherical (open bars) and polarized cells (closed bars) assessed using Nomarski optics for 100 cells per sample. Mean±s.e.m. of three experiments.