![Glucose metabolism stimulates exocytosis and ER Ca2+ uptake in δ-cells. Exocytosis and ER Ca2+ uptake in δ-cells are stimulated by glucose metabolism or forskolin. (A) Exocytosis (measured as increases in membrane capacitance, bottom traces, ΔCm) triggered by 300-ms depolarizations from −70 mV to 0 mV (top) in δ-cells exposed to indicated experimental conditions (red). The black traces show the exocytotic responses triggered by identical pulses in the same cells exposed to 1 mM glucose alone. The experiments were conducted using perforated patch whole-cell configuration. (B) Summary of exocytotic response (IRP) in δ-cells perfused with extracellular solutions containing glucose (1 mM and 20 mM), forskolin (2 µM), and 10 mM mannoheptulose in the presence of 20 mM glucose. *, P < 0.05 vs. 1 mM glucose and †, P < 0.05 vs. 20 mM glucose alone. Data are mean values ± SEM of indicated number of independent experiments (n) from 2–14 animals. (C) Increase in [Ca2+]i (ΔF) triggered by photorelease of caged InsP3 precursor in δ-cells preincubated at 1 mM (black) or 20 mM glucose (red) for >1 h. Photoliberation was effected by a flash of UV light as indicated. Traces are representative responses of similar independent experiments (n = 4 for 1 mM and 20 mM glucose). (D) Summary of data in C. *, P < 0.05 vs. 1 mM glucose. Data are mean values ± SEM of four independent experiments from two to four animals for each experimental condition. (E) As in C but shows the δ-cell exocytosis (ΔCm) in response to photoliberation of InsP3. Pre-incubation glucose concentrations are as indicated. The dotted lines indicate the slope of initial capacitance increase. (F) Summary of the initial exocytotic rate (δCm/δt) following photorelease of InsP3 in δ-cells preincubated at 1 mM or 20 mM glucose for >1 h. *, P < 0.05 vs. 1 mM glucose. The exocytotic rate was calculated by differentiating the rising slope of capacitance increase in response to increases in cytosolic InsP3. Data are mean values ± SEM of four independent experiments from two to four animals for each experimental condition. In C–F, experiments were conducted using standard whole-cell technique without addition of cAMP in the intracellular solution.](https://cdn.rupress.org/rup/content_public/journal/jgp/151/9/10.1085_jgp.201912351/10/jgp_201912351_fig6.jpeg?Expires=1767786877&Signature=qvXtYGtqBf~5giFYFfAvPVo4ZVqfjN0uhhwSEFme0vPFGt2Lw9gQe8FqsL5ux8vOcaKX2b98RW4N6FDDz5KKZXp9~FxeX1cMD-T81~gF85nw4-l3pGHCSLNXDh5mQBkurRKC8QwBYqLEPwemRDx7xDyFd3Gep98EzSfXUMPLH1hyHRQBE3U2ltYAXLiZOpWzor1OjpihPrEb8KTNSktnROpnZuMk~nFwtoqsSL9DZtOYuVHCHgRdpSDtl1ttby8xcSOYzHPv54l4lWcJwlbv4yeSObXJayFgOYj5XoeRRTueOqHartblpx6xliBSygNEcOtljFFA8UwknypB6-JmmA__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Glucose metabolism stimulates exocytosis and ER Ca2+ uptake in δ-cells. Exocytosis and ER Ca2+ uptake in δ-cells are stimulated by glucose metabolism or forskolin. (A) Exocytosis (measured as increases in membrane capacitance, bottom traces, ΔCm) triggered by 300-ms depolarizations from −70 mV to 0 mV (top) in δ-cells exposed to indicated experimental conditions (red). The black traces show the exocytotic responses triggered by identical pulses in the same cells exposed to 1 mM glucose alone. The experiments were conducted using perforated patch whole-cell configuration. (B) Summary of exocytotic response (IRP) in δ-cells perfused with extracellular solutions containing glucose (1 mM and 20 mM), forskolin (2 µM), and 10 mM mannoheptulose in the presence of 20 mM glucose. *, P < 0.05 vs. 1 mM glucose and †, P < 0.05 vs. 20 mM glucose alone. Data are mean values ± SEM of indicated number of independent experiments (n) from 2–14 animals. (C) Increase in [Ca2+]i (ΔF) triggered by photorelease of caged InsP3 precursor in δ-cells preincubated at 1 mM (black) or 20 mM glucose (red) for >1 h. Photoliberation was effected by a flash of UV light as indicated. Traces are representative responses of similar independent experiments (n = 4 for 1 mM and 20 mM glucose). (D) Summary of data in C. *, P < 0.05 vs. 1 mM glucose. Data are mean values ± SEM of four independent experiments from two to four animals for each experimental condition. (E) As in C but shows the δ-cell exocytosis (ΔCm) in response to photoliberation of InsP3. Pre-incubation glucose concentrations are as indicated. The dotted lines indicate the slope of initial capacitance increase. (F) Summary of the initial exocytotic rate (δCm/δt) following photorelease of InsP3 in δ-cells preincubated at 1 mM or 20 mM glucose for >1 h. *, P < 0.05 vs. 1 mM glucose. The exocytotic rate was calculated by differentiating the rising slope of capacitance increase in response to increases in cytosolic InsP3. Data are mean values ± SEM of four independent experiments from two to four animals for each experimental condition. In C–F, experiments were conducted using standard whole-cell technique without addition of cAMP in the intracellular solution.
