FIG. 7.

Characteristics of Ca²⁺ uptake by the ER in response to activation of cell metabolism and during blockade of Ca²⁺ influx through voltage-dependent Ca²⁺ channels. [Ca²⁺]_ER (D4ER) was measured in β-cells from SERCA3^+/+ mice perifused with a Ca²⁺-free medium (Ca0-EGTA) throughout (A–E) or only at the beginning of the experiment (F). A and C–F: The glucose concentration was increased from 0 (G0) to 20 mmol/L (G20) before the addition of 250 µmol/L Dz (A) or 5 mmol/L azide (D), or the readmission of 2.5 mmol/L CaCl₂ (Ca2.5) (F), or after the application of 20 mmol/L sucrose (C) or 5 mmol/L azide (E). B: The medium was supplemented with 5 mmol/L leucine and 5 mmol/L glutamine (Leu5 + Gln5) when indicated. A–F: ACh (100 µmol/L ) was added at the end of the experiments. Values are means ± SE for 23–44 cells from three experiments with three islet preparations.