Glucose-induced insulin secretion is pulsatile. We investigated how the triggering pathway (rise in β-cell [Ca2+]i) and amplifying pathway (greater Ca2+ efficacy on exocytosis) influence this pulsatility. Repetitive [Ca2+]i pulses were imposed by high K++ diazoxide in single mouse islets. Insulin secretion (measured simultaneously) tightly followed [Ca2+]i changes. Lengthening [Ca2+]i pulses increased the duration but not the amplitude of insulin pulses. Increasing glucose (5–20 mmol/l) augmented the amplitude of insulin pulses without changing that of [Ca2+]i pulses. Larger [Ca2+]i pulses augmented the amplitude of insulin pulses at high, but not low glucose. In conclusion, the amplification pathway ensures amplitude modulation of insulin pulses whose time modulation is achieved by the triggering pathway.
