Figure 1.

Local Ca²⁺ spikes induced by photolysis of caged IP₃ in pancreatic acinar cells. Local increases in [Ca²⁺]_i were induced by photolysis of 5 μM caged IP₃. (A) Ca²⁺ images obtained with a confocal microscope and the high-affinity Ca²⁺ indicator fluo-3. (B) Time courses of [Ca²⁺]_i within the rectangles shown in A. (C) Ca²⁺ images obtained with a cooled CCD camera and the low-affinity Ca²⁺ indicator BTC. (D) Time courses of [Ca²⁺]_i within the rectangles shown in C. Dashed white lines in the black and white photographs shown in A and C indicate the secretory granule region of the cell. Vertical white bars in B and D indicate the times when the images shown in A and C were obtained; the arrow indicates the time of photolysis of caged IP₃ induced by ultraviolet (UV) irradiation.