benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone and fluorexon

In normal pancreatic acinar cells, the oxidant menadione evokes repetitive cytosolic Ca(2+) spikes, partial mitochondrial depolarisation, cytochrome c release and apoptosis. The physiological agonists acetylcholine and cholecystokinin also evoke cytosolic Ca(2+) spikes but do not depolarise mitochondria and fail to induce apoptosis. Ca(2+) spikes induced by low agonist concentrations are confined to the apical secretory pole of the cell by the buffering action of perigranular mitochondria. Menadione prevents mitochondrial Ca(2+) uptake, which permits rapid spread of Ca(2+) throughout the cell. Menadione-induced mitochondrial depolarisation is due to induction of the permeability transition pore. Blockade of the permeability transition pore with bongkrekic acid prevents activation of caspase 9 and 3. In contrast, the combination of antimycin A and acetylcholine does not cause apoptosis but elicits a global cytosolic Ca(2+) rise and mitochondrial depolarisation without induction of the permeability transition pore. Increasing the cytosolic Ca(2+) buffering power by BAPTA prevents cytosolic Ca(2+) spiking, blocks the menadione-elicited mitochondrial depolarisation and blocks menadione-induced apoptosis. These results suggest a twin-track model in which both intracellular release of Ca(2+) and induction of the permeability transition pore are required for initiation of apoptosis.

Topics: Acetylcholine; Amino Acid Chloromethyl Ketones; Animals; Anti-Bacterial Agents; Antifibrinolytic Agents; Antimycin A; Apoptosis; Bongkrekic Acid; Calcium; Calcium Signaling; Caspase 3; Caspase 9; Caspases; Cell Nucleus; Cells, Cultured; Chelating Agents; Cysteine Proteinase Inhibitors; Egtazic Acid; Fluoresceins; Fluorescent Dyes; Membrane Potentials; Mice; Mitochondria; Pancreas; Vasodilator Agents; Vitamin K 3