title: Rapid functional evaluation of beta-cells by extracellular recording of membrane potential oscillations with microelectrode arrays.
abstract: The membrane potential (V                         (m)) of beta-cells oscillates at glucose concentrations between ~6 and 25 mM, i.e. burst phases with action potentials alternate with silent interburst phases generating so-called slow waves. The slow waves drive oscillations of the cytosolic Ca(2+) concentration ([Ca(2+)](c)) and insulin secretion. The length of the bursts correlates with the amount of insulin release. Thus, the fraction of plateau phase (FOPP), i.e. the percentage of time with burst activity, is an excellent marker for beta-cell function and metabolic integrity. Extracellular voltage changes of mouse islets were measured using a microelectrode array (MEA) allowing the detection of burst and interburst phases. At a non-stimulating glucose concentration (3 mM) no electrical activity was detectable while bursting was continuous at 30 mM. The glucose concentration-response (determined as FOPP) curve revealed half-maximal stimulation at 12 ± 1 mM (Hill equation fit). The signal was sensitive to K(ATP) channel modulators, e.g. tolbutamide or diazoxide. Simultaneous recordings of electrical activity and [Ca(2+)](c) revealed congruent bursts and peaks, respectively. The extracellular recordings are in perfect agreement with more time-consuming intracellular electrical recordings. The results provide a 'proof-of-principle' for detection of beta-cell slow waves and determination of the FOPP using extracellular electrodes in a MEA-based system. The method is facile and provides the capability to study the effects of modulators of beta-cell function including possible anti-diabetic drugs in real time. Moreover, the method may be useful for checking the metabolic integrity of human donor islets prior to transplantation.
authors.affiliation: NMI Natural and Medical Science Institute, Department of Electrophysiology, University of Tübingen, Markwiesenstraße 55, 72770 Reutlingen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pfeiffer
authors.forename: Udo
authors.initials: U
authors.lastname: Kraushaar
authors.forename: Martina
authors.initials: M
authors.lastname: Düfer
authors.forename: Sven
authors.initials: S
authors.lastname: Schönecker
authors.forename: Dirk
authors.initials: D
authors.lastname: Haspel
authors.forename: Elke
authors.initials: E
authors.lastname: Günther
authors.forename: Gisela
authors.initials: G
authors.lastname: Drews
authors.forename: Peter
authors.initials: P
authors.lastname: Krippeit-Drews
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003981:Diazoxide; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008839:Microelectrodes; D018408:Patch-Clamp Techniques / Q000295:instrumentation* / Q000379:methods*; D014044:Tolbutamide / Q000494:pharmacology
chemical_list: D000959:Antihypertensive Agents; D007004:Hypoglycemic Agents; D007328:Insulin; D014044:Tolbutamide; D005947:Glucose; D003981:Diazoxide; D002118:Calcium