CYTOSOLIC CALCIUM OSCILLATIONS AND INSULIN RELEASE IN PANCREATIC-ISLETS OF LANGERHANS

Stimulation of insulin release by glucose and other nutrients has been attributed to a rise of cytoplasmic Ca2+([Ca2+](i)). In intact pancre atic islets, this rise is organized in oscillations. Two types of [Ca2 +](i) oscillations are mainly detected. Fast oscillations (frequency o f approximate to 3 min(-1)) are consistently observed, and their durat ion depends on glucose concentration. They are due to a bursting of el ectrical activity and occur synchronously throughout the islet. Slow o scillations (frequency of 0.2 min(-1)) also appear in response to othe r nutrient secretagogues (ketoisocaproate, leucine, isoleucine). They most probably constitute the physiological oscillatory pattern because islets perifused with a solution containing a mixture of amino acids and glucose at concentrations found in the plasma of fed animals showe d the same oscillatory pattern. Slow [Ca2+](i) oscillations may consti tute the framework for pulsatile insulin release observed in vivo.