Active mitochondria surrounding the pancreatic acinar granule region prevent spreading of inositol trisphosphate-evoked local cytosolic Ca2+ signals

Agonist-evoked cytosolic Ca2+ spikes in mouse pancreatic acinar cells are s pecifically initiated in the apical secretory pole and are mostly confined to this region, The role played by mitochondria in this process has been in vestigated. Using the mitochondria-specific fluorescent dyes MitoTracker Gr een and Rhodamine 123, these organelles appeared as a bright belt concentra ted mainly around the secretory granule area. We tested the effects of two different types of mitochondrial inhibitor on the cytosolic Ca2+ concentrat ion using simultaneous imaging of Ca2+-sensitive fluorescence (Fura 2) and electrophysiology, When carbonyl cyanide m-chlorophenylhydrazone (CCCP) was applied in the presence of the Ca2+-releasing messenger inositol 1,4,5-tri sphosphate (IP3), the local repetitive Ca2+ responses in the granule area w ere transformed into a global rise in the cellular Ca2+ concentration. In t he absence of IP3, CCCP had no effect on the cytosolic Ca2+ levels. Antimyc in and antimycin + oligomycin had the same effect as CCCP, Active mitochond ria, strategically placed around the secretory pole, block Ca2+ diffusion f rom the primary Ca2+ release sites in the granule-rich area in the apical p ole to the basal part of the cell containing the nucleus. When mitochondria l function is inhibited, this barrier disappears and the Ca2+ signals sprea d all over the cytosol.