Ca2+ and electrolyte mobilization following agonist application to the pancreatic β cell line HIT

Ikuko Nakagaki, Sadao Sasaki, Seiki Hori, Hisao Kondo

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

We have investigated intracellular Ca2+ mobilization in oscillations of cytoplasmic Ca2+ in response to glucagon-like peptide 1 (GLP-1) and glucose in clonal HIT insulinoma cells with a confocal laser-scanning microscope (CLSM). We also used electron probe X-ray microanalysis to determine the GLP-1- and glucose-induced changes in electrolyte levels in the cytoplasm and insulin granules of the cells. GLP-1 produced 10- to 35-s duration oscillations in cytoplasmic Ca2+ concentration ([Ca2+](i)), both with and without Ca2+ in the extracellular solution, suggesting that Ca2+ is mobilized from intracellular Ca2+ stores, namely secretory granules. Glucose caused 1- to 3-min duration oscillatory increases in [Ca2+](i) when the extracellular solution contained Ca2+. When the cells were cultured without Ca2+ (no Ca2+ added, 1 mM EGTA), an oscillatory [Ca2+](i) increase of amplitude and short duration (12-35 s) was produced by 11 mM glucose, and the oscillation was inhibited by ruthenium red. X-ray microanalysis showed that stimulation with glucose increased the total Ca concentration in the cytoplasm and decreased it in the insulin granules with and without Ca2+ in the extracellular solution. The application of glucose significantly decreased K, and increased Na and Cl in the cytoplasm when the extracellular solution contained Ca2+. Our result also suggests that the [Ca2+](i) oscillation induced by glucose is involved in the release of Ca2+ from intracellular Ca2+ stores through the ryanodine receptor, which is blocked by ruthenium red, and/or through the inositol trisphosphate receptor that may be present in the membrane of insulin granules.

Original languageEnglish
Pages (from-to)828-834
Number of pages7
JournalPflugers Archiv European Journal of Physiology
Volume440
Issue number6
DOIs
Publication statusPublished - Jan 1 2000
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

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