FIG. 3.

Calcium imaging of mouse islets. A: Application of 20 μmol/l tolbutamide (Tolb) to islets superfused with 2.8 mmol/l glucose increases Ca²⁺_c levels that are lower upon a second tolbutamide application. B: In contrast, the addition of 1 μmol/l KB-R7943 significantly increases the magnitude of Ca²⁺_c elevation observed during the second application of tolbutamide. KB-R7943 does not increase Ca²⁺_c levels when applied alone in the presence of 2.8 mmol/l glucose. Ci: Grouped data showing that KB-R7943 significantly increases Ca²⁺_c levels (*P < 0.05, n = 6–11 islets) in the presence of tolbutamide or KCl. Cii: Grouped data showing that in the absence of the tolbutamide or KCl stimulatory signal, KB-R7943 does not increase Ca²⁺_c (n = 6–9 islets). D: Grouped data indicating that the rate at which Ca²⁺_c returned to basal levels is slower in the presence of KB-R7943 for both tolbutamide and KCl (*P < 0.05, n = 6–9 islets). E: Increasing glucose from 2.8 to 11.1 mmol/l elicited increases in Ca²⁺_c, whereas 1 μmol/l KB-R7943 did not increase Ca²⁺_c at 2.8 mmol/l glucose but significantly increased Ca²⁺_c in 11.1 mmol/l glucose when compared with 11.1 mmol/l glucose alone. Grouped data showing that 1 μmol/l KB-R7943 significantly increased the peak (Δpeak) (Fi) and average Ca²⁺_c (AUC) in response to 11.1 mmol/l glucose (Fii). *P < 0.05, n = 9 islets per group.