Effects of PPADS and extracellular Ca2+ removal on calcium responses to 2-MeSATP. A-B. Calcium images showing a group of chromaffin cells during stimulation with 20 μM 2-MeSATP in presence of extracellular calcium (A) and during stimulation in the virtual absence of extracellular calcium ("2-MeSATP +EGTA", B); C-D. The cells were subsequently superfused with a Ca2+-containing solution and challenged with 2-MeSATP, in the absence (C) or presence of 50 μM PPADS ("2-MeSATP +PPADS", D). Calibration bar: 50 μm. More in the legend to Fig. 1(A-D); E. Time courses of changes in F340/F380 fluorescence ratio for two representative cells (cells 1 and 2, also depicted in A-D). The lines denote superfusions with 2-MeSATP, PPADS or EGTA-containing solution. The responses are representative of data from 3 experiments.