Figure 1. Prolonged hyperglycemia increases ATP-evoked Ca²⁺ influx in RF/6A cells. RF/6A cells were treated for 96 h with 5.5 mM glucose (NG), NG plus 24.5 mM D-mannitol, or 30 mM glucose (HG), and the fluorescence intensity was analyzed as described in Methods. A-C: Images of fluo-3-loaded cells pre-incubated with NG, NG plus D-mannitol, or HG. D-F: Images of peak [Ca²⁺]i responses acquired during ATP (200 μM) stimulation in Ca²⁺-free saline (Ca²⁺ release). G-I: Images of cells after the re-addition of 1.8 mM Ca²⁺ to the extracellular medium (Ca²⁺ entry). J: Average baseline [Ca²⁺]i, peak [Ca²⁺]i in Ca²⁺-free saline, and sustained [Ca²⁺]i after the re-addition of extracellular Ca²⁺. Each bar represents the average (SD) of 30–35 cells. * p<0.05 versus NG or NG + D-mannitol.