Metformin Inhibits Mouse Islet Insulin Secretion and Alters Intracellular Calcium in a Concentration-Dependent and Duration-Dependent Manner near the Circulating Range

Figure 4

Metformin impairs glucose-stimulated [Ca²⁺]_i responses. (a–c) Glucose-stimulated [Ca²⁺]_i responses (Mean +/− SEM) from islets treated for 1 day with 20 μM (a), 200 μM (b), and 1 mM metformin (c). (d–f) Glucose-stimulated [Ca²⁺]_i responses (Mean +/− SEM) in islets treated for 2 days with 20 μM (d), 200 μM (e), and 1 mM metformin (f). (g–i) Glucose-stimulated [Ca²⁺]_i responses (Mean +/− SEM) in islets treated for 3 days with 20 μM (g), 200 μM (h), and 1 mM metformin (i). A total of 436 individual islet traces were studied in two trials combined for analysis; 17–33 islets were recorded for each metformin condition. Phases of the calcium response are labeled only in (a) but occur similarly for each panel. Statistically different means in [Ca²⁺]_i between untreated and metformin-treated islets are reported as follows: N.S. = not significant, , , , .