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

Research output: Contribution to journalArticle

19 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)443-448
Number of pages6
JournalPflügers Archiv European Journal of Physiology
Volume422
Issue number5
DOIs
StatePublished - Feb 1 1993
Externally publishedYes

Fingerprint

Apamin
Calcium-Activated Potassium Channels
Insulin-Secreting Cells
Guanosine Triphosphate
Demonstrations
Cells
B-Lymphocytes
Tolbutamide
Tetraethylammonium
Clonidine
Carbachol
Membrane Potentials
Action Potentials
Chemical activation
Pharmacology
Membranes
Glucose

Keywords

  • Apamin
  • Ca
  • Insulin
  • K-channel
  • Pancreas

ASJC Scopus subject areas

  • Physiology

Cite this

Demonstration of a novel apamin-insensitive calcium-activated K+ channel in mouse pancreatic B cells. / Ämmälä, Carina; Bokvist, Krister; Larsson, Olof; Berggren, Per Olof; Rorsman, Patrik.

In: Pflügers Archiv European Journal of Physiology, Vol. 422, No. 5, 01.02.1993, p. 443-448.

Research output: Contribution to journalArticle

Ämmälä, Carina ; Bokvist, Krister ; Larsson, Olof ; Berggren, Per Olof ; Rorsman, Patrik. / Demonstration of a novel apamin-insensitive calcium-activated K+ channel in mouse pancreatic B cells. In: Pflügers Archiv European Journal of Physiology. 1993 ; Vol. 422, No. 5. pp. 443-448.
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