Fig. 2. Mitochondrial Ca²⁺ uptake, measured with Rhod-2, following maximal ACh (10 µM)-elicited Ca²⁺ release from the endoplasmic reticulum. (A) Transmitted light picture showing the cell under investigation, with the three areas of interest identified by the three coloured circles. The length of the red bar represents 10 µm. (B) Autofluorescence image showing mitochondrial localization. (C) Six images showing mitochondrial Ca²⁺ concentration. Image 1 shows the situation just before the start of stimulation. Image 2 shows that immediately after ACh application, there was Ca²⁺ uptake into mitochondria very close to the apical membrane. A little later, the whole perigranular mitochondrial belt was revealed (images 3 and 4) and finally (images 5 and 6) all mitochondria in the cell had taken up Ca²⁺. (D) The time course of the mitochondrial Ca²⁺ uptake in the three regions identified in (A) using the appropriate colour coding. The main part of the figure represents a short time segment of the more complete traces shown in the inset. The time scale relates to the expanded traces labeled with the numbers 1–6, corresponding to the images in (C).