Cultured MKs were incubated with PE-GPIb antibody and FITC-FGN (100 μg/mL) in the presence and absence of TRAP (50 μmol/L) for the indicated time intervals before the addition of EDTA (10 mmol/L) or ethidium bromide (50 μg/mL). FITC-fluorescence histograms were generated from the MK population. Total FITC-FGN binding was defined as the MFI of TRAP-stimulated samples in the absence of EDTA or ethidium bromide. The fraction of FITC-FGN that was irreversibly bound or internalized was determined from the reduction in MFI in the presence of EDTA or ethidium bromide, respectively, as described in Materials and Methods. Results are the mean ± SEM for n = 3 in each group.