GLUCOSE-INDUCED AMPLITUDE REGULATION OF PULSATILE INSULIN-SECRETION FROM INDIVIDUAL PANCREATIC-ISLETS

The insulin secretory response to glucose was studied in single pancreatic islets isolated from ob/ob mice and rats. The perifusate from an individual islet was collected during 18-s periods and analyzed for insulin with an ELISA technique. Increase of the glucose concentration from 3 to greater-than-or-equal-to 5.5 mM resulted in pulses of insulin release often originating from the basal level and having a frequency of 0.4/min. Glucose regulation of insulin release from the individual islet was manifested by alterations of the amplitudes of the pulses but not of their frequency. It is concluded that the large amplitude oscillations of cytoplasmic Ca2+ known to occur in the pancreatic beta-cells have their counterpart in pulses of insulin release and that glucose stimulation of the secretory activity may be the result of recruitment of more beta-cells into an oscillatory state.