Fig. 7. FFA deplete ER calcium stores in β-cells. (A) INS-1E cells were cultured for 24 hours in the presence of oleate (O, red line), palmitate (P, green line) or control (C, black line) at a glucose concentration of 11 mM. The intracellular Ca²⁺ concentration was measured at baseline and following acute thapsigargin stimulation (arrow). The traces shown are the means of 5-6 independent experiments (278-368 cells/experiment). (B) Following infection with an ER-targeted aequorin-encoding adenovirus, INS-1E cells were cultured for 3-24 hours in the presence of oleate (O, red line), palmitate (P, green line), an equimolar mixture of oleate and palmitate (OP, blue line) or control (C, black line) at a glucose concentration of 11 mM. Prior to the measurements, cells were depleted of Ca²⁺ and the aequorin was reconstituted with coelenterazine n in Ca²⁺-free KRBB. External CaCl₂ (1.5 mM) was then reintroduced at t=20 seconds to allow the reestablishment of ER Ca²⁺ levels. The results are the means ± s.e.m. of four independent experiments. Bold diamond symbols represent Ca²⁺ values significantly different from control condition (P<0.05).