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Title: Differential patterns of glucose-induced electrical activity and intracellular calcium responses in single mouse and rat pancreatic islets
Authors: Antunes, Célia M. 
Salgado, António P. 
Rosário, Luís M. 
Santos, Rosa M. 
Issue Date: Dec-2000
Publisher: American Diabetes Association
Citation: Diabetes. 49:12 (2000) 2028-2038
Abstract: Although isolated rat islets are widely used to study in vitro insulin secretion and the underlying metabolic and ionic processes, knowledge on the properties of glucose-induced electrical activity (GIEA), a key step in glucose-response coupling, has been gathered almost exclusively from microdissected mouse islets. Using a modified intracellular recording technique, we have now compared the patterns of GIEA in collagenase-isolated rat and mouse islets. Resting membrane potentials of rat and mouse beta-cells were approximately -50 and -60 mV, respectively. Both rat and mouse beta-cells displayed prompt membrane depolarizations in response to glucose. However, whereas the latter exhibited a bursting pattern consisting of alternating hyperpolarized and depolarized active phases, rat beta-cells fired action potentials from a nonoscillating membrane potential at all glucose concentrations (8.4-22.0 mmol/l). This was mirrored by changes in the intracellular Ca2+ concentration ([Ca2+]i), which was oscillatory in mouse and nonoscillatory in rat islets. Stimulated rat beta-cells were strongly hyperpolarized by diazoxide, an activator of ATP-dependent K+ channels. Glucose evoked dose-dependent depolarizations and [Ca2+]i increases in both rat (EC50 5.9-6.9 mmol/l) and mouse islets (EC50 8.3-9.5 mmol/l), although it did not affect the burst plateau potential in the latter case. We conclude that there are important differences between beta-cells from both species with respect to early steps in the stimulus-secretion coupling cascade based on the following findings: 1) mouse beta-cells have a larger resting K+ conductance in 2 mmol/l glucose, 2) rat beta-cells lack the compensatory mechanism responsible for generating membrane potential oscillations and holding the depolarized plateau potential in mouse beta-cells, and 3) the electrical and [Ca2+]i dose-response curves in rat beta-cells are shifted toward lower glucose concentrations. Exploring the molecular basis of these differences may clarify several a priori assumptions on the electrophysiological properties of rat beta-cells, which could foster the development of new working models of pancreatic beta-cell function
ISSN: 0012-1797
DOI: 10.2337/diabetes.49.12.2028
Rights: openAccess
Appears in Collections:FCTUC Ciências da Vida - Artigos em Revistas Internacionais

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