Fig. 2. Fragmentation of the ER reduces the rate of [Ca²⁺]_i increase. (A) Examples of the Ca²⁺ increase in individual acini obtained from WT (solid traces) and PERK^-/- mice (dashed traces) stimulated with 5 or 25 µM carbachol, as indicated by the bars. WT () and PERK^-/- () pancreatic acinar cells were stimulated with different concentrations of carbachol and the extent (B) and rate (C) of the [Ca²⁺]_i increase were measured. The results are the mean ± s.e.m. of three acinar preparations with at least four experiments with every cell preparation. Similar findings were observed in the presence (1 mM) and absence (no Ca²⁺ and 0.1 EGTA) of Ca²⁺_o and therefore results obtained in the presence and absence of Ca²⁺_o were averaged in B and C.