REAL-TIME ELECTROCHEMICAL DETECTION OF 5-HT INSULIN SECRETION FROM SINGLE PANCREATIC-ISLETS - EFFECT OF GLUCOSE AND K+ DEPOLARIZATION/

We report a highly sensitive electrochemical approach suitable for the real dme measurement of insulin release from single islets of Langerh ans, the functional endocrine units in the pancreas. The method is bas ed on tile detection of the insulin surrogate 5-hydroxytryptamine (5-H T) by carbon fibre microelectrodes implanted in the islets. Based on t he combination of this novel approach with the simultaneous microfluor ometric recording of cytosolic free Ca2+ concentration ([Ca2+](i)), we demonstrate that glucose-stimulated islets secrete 5-HT/insulin in a pulsatile fashion under physiological conditions and that this activit y is encoded by synchronous [Ca2+](i) oscillations. The sensitivity to detect variations in minute amounts of secreted materials is partiall y conferred by the fact that the tracer is released into a relatively confined space (the intraislet interstitial space). (C) 1996 Academic Press, Inc.