Glucose induces a biphasic increase in cytosolic ATP/ADP ratio.

<p><b><i>A</i></b>: The effects of high (17mM) glucose on [ATP/ADP]_cyt (reported with <i>Perceval</i>), [Ca²⁺]_cyt (Fura-Red) and V_m were measured in a single β-cell (representative of n = 30 cells). The voltage down-strokes were elicited by 10 ms 10 pA current injections applied every 20 s to monitor the input resistance which increased upon the elevation of [ATP/ADP]_cyt. <b><i>Inset</i></b>: Pseudo-colour images of the patched cell cluster presenting pixel-to-pixel ratios at the time points indicated by arrows (<i>i–vi</i>). ROI is indicated with red oval. Note that a cell expressing high levels of <i>Perceval</i> (just below the ROI) was deliberately excluded from analysis. <b><i>B</i></b>: Characteristic times and amplitudes of glucose-induced [ATP/ADP]_cyt increase in β-cells (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039722#pone-0039722-g001" target="_blank">Fig. 1A</a>; n = 30). The data were normalised to the width of the range of [ATP/ADP]_cyt change (ΔF_max), measured as the difference in <i>Perceval</i> fluorescence between the peak point at 17 mM glucose and the point corresponding to application of 2 µM FCCP. Depolarisation and onset of electrical activity was taken as zero of the time axis. The change in [ATP/ADP]_cyt (ΔF/ΔF_max) at each point is significant <i>vs</i> every other point (p<0.01, Wilcoxon's paired test).