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Pflügers Archiv

, Volume 422, Issue 5, pp 443–448 | Cite as

Demonstration of a novel apamin-insensitive calcium-activated K+ channel in mouse pancreatic B cells

  • Carina Ämmälä
  • Krister Bokvist
  • Olof Larsson
  • Per -Olof Berggren
  • Patrik Rorsman
Transport Processes, Metabolism and Endocrinology; Kidney, Gastrointestinal Tract, and Exocrine Glands

Abstract

The whole-cell configuration of the patchclamp technique was used to characterize the biophysical and pharmacological properties of an oscillating K+-current that can be induced by intracellular application of GTP[γS] in mouse pancreatic B cells (Ämmälä et al. 1991). These K+ conductance changes are evoked by periodic increases in the cytoplasmic Ca2+ concentration ([Ca2+]i) and transiently repolarize the B cell, thus inhibiting action-potential firing and giving rise to a bursting pattern. GTP[γS]-evoked oscillations in K+ conductance were reversibly suppressed by a high (300 μM) concentration of carbamylcholine. By contrast, α2-adrenoreceptor stimulation by 20 μM clonidine did not interfere with the oscillatory behaviour but evoked a small sustained outward current. At 0 mV membrane potential, the oscillating K+-current elicited by GTP[γS] was highly sensitive to extracellular tetraethylammonium (TEA; 70% block by 1 mM). The TEA-resistant component, which carried approximately 80% of the current at −40 mV, was affected neither by apamin (1 μM) nor by tolbutamide (500 μM). The current evoked by internal GTP[γS] was highly selective for K+, as demonstrated by a 51-mV change in the reversal potential for a sevenfold change in [K+]o. Stationary fluctuation analysis indicated a unitary conductance of 0.5 pS when measured with symmetric (≈ 140mM) KCl solutions. The estimated singlechannel conductance with physiological ionic gradients is 0.1 pS. The results indicate the existence of a novel Ca2+-gated K+ conductance in pancreatic B cells. Activation of this K+ current may contribute to the generation of the oscillatory electrical activity characterizing the B cell at intermediate glucose concentrations.

Key words

K+-channel Ca2+ Apamin Pancreas Insulin 

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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Carina Ämmälä
    • 1
  • Krister Bokvist
    • 1
  • Olof Larsson
    • 1
  • Per -Olof Berggren
    • 1
  • Patrik Rorsman
    • 1
  1. 1.Department of Medical BiophysicsGöteborgs UniversitetGöteborgSweden

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