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 pancreatic islets, this rise is organized in oscillations. Two types of [Ca2+]i oscillations are mainly detected. Fast oscillations (frequency of approximately equal to 3 min-1) are consistently observed, and their duration depends on glucose concentration. They are due to a bursting of electrical activity and occur synchronously throughout the islet. Slow oscillations (frequency of 0.2 min-1) also appear in response to other 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 showed the same oscillatory pattern. Slow [Ca2+]i oscillations may constitute the framework for pulsatile insulin release observed in vivo.