FIG. 7.
A 15-week HFD treatment inhibits depolarization-evoked exocytosis. A: Representative recordings of exocytosis during a train of 50-ms (10 Hz) depolarizations from −70 mV to 0 mV in ND (black) and HFD (gray) β-cells. B: Relationship between integrated current charge (ΣQ) and changes in membrane capacitance (ΣΔCm) during the train of twenty 50-ms depolarizations (10 Hz). The responses during the four first depolarizations (not associated with exocytosis) are not shown. The lines superimposed on the data points indicate the slopes of the relationships. C: Representative increases in cell capacitance evoked by a train of ten 500-ms (1 Hz) depolarizations from −70 mV to 0 mV in ND (black) and HFD (gray) β-cells. D: Increase in cell capacitance for each pulse during the train of 500-ms depolarizations in ND (black) and HFD (gray) β-cells. Mean values ± SEM for 75 (ND) and 61 (HFD) cells. *P < 0.06. E: Total capacitance increments (in fF) following the train of 50-ms (black) and 500-ms (gray) pulses. Data are means ± SEM for at least 61–75 β-cells from six animals from each group in the long pulses experiment and for at least 23 β-cells from three animals from each group in the short pulses experiment. **P < 0.005. F: Average rates of optically measured release of vesicles by discharge of fluorescent IAPP-mCherry cargo during a 1,000-ms membrane depolarization to 0 mV. Data are means ± SEM for 5 and 6 cells from two animals in each group for both ND (black) and HFD (gray) β-cells. *P < 0.05.