Cytoplasmic calcium transients due to single action potentials and voltage-clamp depolarizations in mouse pancreatic B-cells

Patrik Rorsman, Carina Ämmälä, Per Olof Berggren, Krister Bokvist, Olof Larsson

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Abstract

Changes in the cytoplasmic free calcium concentration ([Ca2+]i) in pancreatic B-cells play an important role in the regulation of insulin secretion. We have recorded [Ca2+]i transients evoked by single action potentials and voltage-clamp Ca2+ currents in isolated B-cells by the combination of dual wavelength emission spectrofluorimetry and the patch-clamp technique. A 500-1000 ms depolarization of the B-cell from -70 to -10 mV evoked a transient rise in [Ca2+]i from a resting value of ∼ 100 nM to a peak concentration of 550 nM. Similar [Ca2+]i changes were associated with individual action potentials. The depolarization-induced [Ca2+]i transients were abolished by application of nifedipine, a blocker of L-type Ca2+ channels, indicating their dependence on influx of extracellular Ca2+. Following the voltage-clamp step, [Ca2+]i decayed with a time constant of ∼2.5 s and summation of [Ca2+]i occurred whenever depolarizations were applied with an interval of <2 s. The importance of the Na+ -Ca2+ exchange for B-cell [Ca2+]i maintenance was evidenced by the demonstration that basal [Ca2+]i rose to 200 nM and the magnitude of the depolarization-evoked [Ca2+]i transients was markedly increased after omission of extracellular Na+. However, the rate by which [Ca2+]i returned to basal was not affected, suggesting the existence of additional [Ca2+]i buffering processes.

Original languageEnglish
Pages (from-to)2877-2884
Number of pages8
JournalEMBO Journal
Volume11
Issue number8
StatePublished - Dec 1 1992
Externally publishedYes

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Keywords

  • B-cell
  • Ca channels
  • Cytoplasmic Ca
  • Insulin secretion
  • Na-Ca exchange

ASJC Scopus subject areas

  • Genetics
  • Cell Biology

Cite this

Rorsman, P., Ämmälä, C., Berggren, P. O., Bokvist, K., & Larsson, O. (1992). Cytoplasmic calcium transients due to single action potentials and voltage-clamp depolarizations in mouse pancreatic B-cells. EMBO Journal, 11(8), 2877-2884.