Cytosolic and endoplasmic reticulum Ca2+ concentrations determine the extent and the morphological type of apoptosis, respectively.

During apoptosis, an increase in cytosolic Ca(2+) concentration ([Ca(2+)](c)) accompanies the depletion of endoplasmic reticulum (ER). The actual roles of each of the two events in apoptosis are difficult to understand. In this work, we have modulated the basal [Ca(2+)](c) and the thapsigargin (THG)-dependent reticular flux (i.e., by chelating extracellular Ca(2+) or by modulating intracellular Ca(2+) by 3-aminobenzamide [3-ABA]). We have found that these treatments alter these Ca(2+) parameters in a differential way and, accordingly, affect apoptosis differentially. We have found that the increase in [Ca(2+)](c) is related to the extent of apoptosis, whereas the ER depletion affects the apoptotic nuclear morphology by shifting it towards the cleavage mode.