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This Article Full Text Full Text (PDF) All Versions of this Article: 568/1/137    most recent jphysiol.2005.093740v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Best, L Search for Related Content PubMed PubMed Citation Articles by Best, L

¹ Department of Medicine, University of Manchester, Oxford Road, Manchester, M13 9WL, UK

A rise in glucose concentration depolarizes the ß-cell membrane potential leading to electrical activity and insulin release. It is generally believed that closure of K_ATP channels underlies the depolarizing action of glucose, though work from several laboratories has indicated the existence of an additional anionic mechanism. It has been proposed that glucose activates a volume-regulated anion channel, generating an inward current due to Cl^– efflux. This mechanism requires that intracellular [Cl^–] is maintained above its electrochemical equilibrium. This hypothesis was tested in rat ß-cells by varying [Cl^–] in the patch pipette solution using the Cl^–-permeable antibiotic amphotericin B to allow Cl^– equilibration with the cell interior. Under such conditions, a depolarization and electrical activity could be evoked by 16 mM glucose with pipette solutions containing 80 or 150 mM Cl^–. At 40 or 20 mM Cl^–, a subthreshold depolarization was usually observed, whilst further reduction to 12 or 6 mM abolished depolarization, in some cases leading to a glucose-induced hyperpolarization. With a pipette solution containing gramicidin, which forms Cl^–-impermeable pores, glucose induced a depolarization and electrical activity irrespective of [Cl^–] in the pipette solution. Under the latter conditions, glucose-induced electrical activity was prevented by bumetanide, an inhibitor of the Na⁺–K⁺–2Cl^– co-transporter. This inhibition could be overcome by the use of amphotericin B with a high [Cl^–] pipette solution. These findings suggest that the maintenance of high intracellular [Cl^–] in the ß-cell is an important determinant in glucose-induced depolarization, and support the hypothesis that ß-cell stimulation by glucose involves activation of the volume-regulated anion channel and generation of an inward Cl^– current.

(Received 28 June 2005; accepted after revision 12 July 2005; first published online 14 July 2005)
Corresponding author L. Best: Multipurpose Building, Manchester Royal Infirmary, Oxford Road, Manchester, M13 9WL, UK. Email: len.best{at}cmmc.nhs.uk