Using microfluorescence in combination with image-analysis techniques we monitored intracellular calcium ([Ca2+]i) dynamics in mouse islets of Langerhans loaded with fura-2 and recorded in vivo. [Ca2+]i oscillates in the glycaemias range 5–10 mM, the duration of the oscillations being directly proportional to the blood glucose concentration. The analysis of different areas within the same islet shows that [Ca2+]i oscillations are synchronous throughout the islet. These results show that in vivo, individual islets of Langerhans behave as a functional syncytium and suggest the existence of secretory pulses of insulin.
