Figure 5.

Deficiency of Hv1 limits membrane depolarization and results in disassociation between calcium signaling and insulin secretion. A and B, representative curves (A) and average traces (B) of GSCa from islets isolated from WT and KO mice. Cellular Ca²⁺ levels in isolated islets were measured by Fura-2 fluorescence; islets were kept at 2.8 mm glucose before switching to stimulation by 16.7 mm glucose, as indicated above the traces. C, mean values of cellular Ca²⁺ levels for baseline under basal conditions. Data are means ± S.E. ***, p < 0.001, KO versus WT. D–F, mean values of cellular Ca²⁺ levels at peaks (D), mean time of duration (E), and mean time to peak (F) after stimulation with glucose (final concentration, 16.7 mm). n = 6/genotype, 2–5 islets/experiment. Data are means ± S.E. ***, p < 0.001, KO versus WT. G and H, membrane potential changes of isolated islet β-cells during glucose stimulation were monitored by DiBAC₄(3) fluorescence (G) and AUC (H). Isolated islet β-cells from WT and KO mice were kept at 2.8 mm glucose before switching to stimulation by 16.7 mm glucose, as indicated above the traces. Data are means ± S.E. ***, p < 0.001, KO versus WT.