FIG. 6.

Effects of IP₃ receptor activation on the ER Ca²⁺ depletion and unfolded protein response activation evoked by SERCA inhibition. A and B: D1ER cameleon measurements of the luminal ER Ca²⁺ release induced by 1 μmol/l thapsigargin, with or without simultaneous addition of 100 μmol/l carbachol (Cch) (n = 10 and 14 cells, respectively). C: Effects of 1 μmol/l thapsigargin administered during exposure to 100 μmol/l Cch (n = 8 cells). D: Effects of 100 μmol/l Cch administered in the presence of 1 μmol/l thapsigargin (n = 9 cells). Note the acceleration of ER Ca²⁺ depletion in cells that had not yet reached a stable depleted state (arrow). E: Phosphorylation of PERK and eIF2α in 25 mmol/l glucose-cultured MIN6 cells was examined at the time points indicated. F: Quantification of Western blots for PERK and eIF2α phosphorylation. Similar results from experiments conducted in 5 and 25 mmol/l glucose were pooled (n = 6, #P < 0.05 vs. control). □, control; , 100 μmol/l Cch; ▪, 1 μmol/l thapsigargin; , thapsigargin + Cch. (Please see http://dx.doi.org/10.2337/db07-1762 for a high-quality digital representation of this figure).