Fig. 6. FGF-2 externalization is not limited by the availability of cell surface HSPGs. CHO_FGF-2-GFP cells were grown for 18 hours at 37°C in the presence (coloured curves in A and B) or absence (white curves in A and B) of doxicyclin. At the end of the incubation, various amounts of recombinant His₆-tagged FGF-2 were added to the culture medium (green, 0.1 µg/ml; pink, 0.25 µg/ml; blue, 0.5 µg/ml; orange, 1 µg/ml; dark blue, 2 µg/ml) followed by an incubation for 60 minutes at 37°C. The red curves in A and B represent a standard FGF-2 secretion experiment in the absence of exogenously added FGF-2. The cell suspension was processed for the FACS analysis as described in the legend to Fig. 3. In this experiment, affinity-purified anti-FGF-2 antibodies were used to detect both cell surface FGF-2 and FGF-2-GFP. (A) GFP-derived fluorescence. (B) FGF-2 cell surface staining.