Figure 2. Ag-stimulated exocytosis can be monitored with VAMP8-pHl or β-Hex-pHl reporters.

(A) RBL-2H3 cells transfected with VAMP8-pHl and sensitized with anti-DNP IgE were suspended, and fluorescence was monitored spectroscopically. Exocytosis was stimulated by the addition of 100 ng/ml DNP-BSA (Ag), and total fluorophore dequenching was achieved by adding 50 mM NH₄Cl. Raw data were normalized by subtracting baseline fluorescence (t=0) from each subsequent fluorescence value. (B) Cells were prepared and analyzed as in (A), except that β-Hex-pHl was transfected instead of VAMP8-pHl. (C) 100 nM bafilomycin (baf) or vehicle (dimethyl sulfoxide, DMSO) was added as indicated, and data were normalized as for (A).