Fig. 1. Fragmentation of the ER in PERK^-/- cells does not affect reloading of the internal Ca²⁺ stores. WT (A) and PERK^-/- pancreatic acini (B) were stimulated with 1 mM carbachol (Carb) to discharge the agonist-mobilized intracellular Ca²⁺ pool. Reloading was initiated by termination of the stimulated state with 10 µM atropine (Atr). At different times after initiation of reloading the cells were re-stimulated with 10 nM CCK to estimate the extent of reloading, which was calculated as the percentage of the maximal response measured with cells stimulated only with CCK. The upper and lower traces in A and B show the reloading after a 30 second and 10 minute treatment with atropine and the time courses of reloading are plotted in panel (C) for WT () and PERK^-/- cells (). The traces in A,B and the summary in C are the mean (black trace) ± s.e.m. (gray lines) of at least three experiments. All experiments were performed in the presence of 1 mM Ca²⁺_o to enable measurement of the reloading.