Fig. 5. Exocytosis does not necessarily lead to peptide release. (A,C) Simultaneous imaging of VAMP-pHluorin (top) and IAPP-ECFP (lower) in double-transfected cells. The cell (imaged at 10 Hz) was stimulated with a 3 second puff of solution containing 87 mM KCl. Times quoted below the images are relative to the peak in the VAMP-pHluorin signal. (A) Example of a granule (highlighted by a circle) that showed a transient increase in VAMP-pHluorin fluorescence and that culminated in the loss of IAPP-ECFP fluorescence. (B) Fluorescence intensities of IAPP-ECFP (open circles) and VAMP-pHluorin (black squares) within ROIs centered on the granule highlighted in A. (C) Example where the increase in VAMP-pHluorin fluorescence was not associated with the rapid loss of IAPP-ECFP fluorescence. (D) As in B, but for the granule shown in C. (E) Analysis of IAPP-ECFP fluorescence in 28 cells and in A,C. Data in the histogram were derived from traces as in B and D by subtracting the intensity measured at t=5.25 seconds from that at -1.0 second, both averaged over 0.5 second.