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

Citation
I. Nakagaki et al., Ca2+ and electrolyte mobilization following agonist application to the pancreatic beta cell line HIT, PFLUG ARCH, 440(6), 2000, pp. 828-834
Citations number
42
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physiology
Journal title
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
ISSN journal
0031-6768 → ACNP
Volume
440
Issue
6
Year of publication
2000
Pages
828 - 834
Database
ISI
SICI code
0031-6768(200010)440:6<828:CAEMFA>2.0.ZU;2-2
Abstract
We have investigated intracellular Ca2+ mobilization in oscillations of cyt oplasmic Ca2+ in response to glucagon-like peptide 1 (GLP-1) and glucose in clonal HIT insulinoma cells with a confocal laser-scanning microscope (CLS M). We also used electron probe X-ray microanalysis to determine the GLP-1- and glucose-induced changes in electrolyte levels in the cytoplasm and ins ulin granules of the cells. GLP-1 produced 10- to 35-s duration oscillation s in cytoplasmic Ca2+ concentration ([Ca2+](i)), both with and without Ca2 in the extracellular solution, suggesting that Ca2+ is mobilized from intr acellular Ca2+ stores, namely secretory granules. Glucose caused 1- to 3-mi n duration oscillatory increases in [Ca2+](i) when the extracellular soluti on contained Ca2+ When the cells were cultured without Ca2+ (no Ca2+ added, I mM EGTA), an oscillatory [Ca2+](i) increase of amplitude and short durat ion (12-35 s) was produced by 11 mM glucose, and the oscillation was inhibi ted by ruthenium red. X-ray microanalysis showed that stimulation with gluc ose 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 an d Cl in the cytoplasm when the extracellular solution contained Ca2+. Our r esult also suggests that the [Ca2+](i) oscillation induced by glucose is in volved in the release of Ca2+ from intracellular Ca2+ stores through the ry anodine receptor, which is blocked by ruthenium red, and/or through the ino sitol trisphosphate receptor that may be present in the membrane of insulin granules.