F-actin content in quiescent and fMLP-stimulated neutrophils measured by using FITC-phalloidin and a fluorescent plate reader (A) or flow cytometry (B).

Measurements using a fluorescent plate reader demonstrated 20% more F-actin in BM than in circulating neutrophils (P < .05) and a 180% increase after exposure to fMLP for 2 minutes (A). In contrast, the F-actin content of quiescent neutrophils isolated from the BM was similar to that of neutrophils from the circulating blood when measured by flow cytometry. Stimulation with fMLP induced an increase in F-actin content that was similar in neutrophils isolated from either site. n = 5 rats in each group. C indicates circulating; BM, bone marrow.