Oscillation of insulin release by the pancreatic islets was evaluated under stringent Ca 2+ -free conditions for the first time. Isolated single rat islets were exposed to 16·7 mM glucose in the presence of 1·9 mM Ca 2+ , or under the stringent Ca 2+ -free conditions (Ca 2+ omission with 1 mM EGTA, 6 µM forskolin and 100 nM phorbol 12-myristate 13-acetate). Fifteen minutes after the initiation of glucose stimulation, effluent was collected at a 6-s interval, insulin was determined in duplicate

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... y a highly sensitive insulin radioimmunoassay, and oscillation and pulsatility of release statistically analyzed. Significant oscillation of insulin release was observed in all islets irrespective of presence and absence of Ca 2+ . Significant pulsatility of release was detected in 7 of 11 islets in the presence of Ca 2+ and three of six islets in the absence of Ca 2+ . In conclusion, high glucose elicits oscillatory insulin release both in the presence and absence of extracellular Ca 2+ .