Mouse β-TC6 Insulinoma Cells: High Expression of Functional α3β4 Nicotinic Receptors Mediating Membrane Potential, Intracellular Calcium, and Insulin Release

In fura 2-loaded N1E-115 cells, regulation of intracellular Ca2+ concentration ([Ca2+]i) following a Ca2+ load induced by 1 μM thapsigargin and 10 μM carbonylcyanide p-trifluoromethyoxyphenylhydrazone (FCCP) was Na+ dependent and inhibited by 5 mM Ni2+. In cells with normal intracellular Na+ concentration ([Na+]i), removal of bath Na+, which should result in reversal of Na+/Ca2+exchange, did not increase [Ca2+]i unless cell Ca2+ buffer capacity was reduced. When N1E-115 cells were Na+ loaded using 100 μM veratridine and 4 μg/ml scorpion venom, the rate of the reverse mode of the Na+/Ca2+ exchanger was apparently enhanced, since an ∼4- to 6-fold increase in [Ca2+]ioccurred despite normal cell Ca2+ buffering. In SBFI-loaded cells, we were able to demonstrate forward operation of the Na+/Ca2+ exchanger (net efflux of Ca2+) by observing increases (∼ 6 mM) in [Na+]i. These Ni2+ (5 mM)-inhibited increases in [Na+]i could only be observed when a continuous ionomycin-induced influx of Ca2+ occurred. The voltage-sensitive dye bis-(1,3-diethylthiobarbituric acid) trimethine oxonol was used to measure changes in membrane potential. Ionomycin (1 μM) depolarized N1E-115 cells (∼25 mV). This depolarization was Na+dependent and blocked by 5 mM Ni2+ and 250–500 μM benzamil. These data provide evidence for the presence of an electrogenic Na+/Ca2+ exchanger that is capable of regulating [Ca2+]i after release of Ca2+ from cell stores.

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Parallel Oscillations of Intracellular Calcium Activity and Mitochondrial Membrane Potential in Mouse Pancreatic B-Cells

Biochemical and Biophysical Research Communications ◽

10.1006/bbrc.1999.1921 ◽

2000 ◽

Vol 267 (1) ◽

pp. 179-183 ◽

Cited By ~ 73

Author(s):

Peter Krippeit-Drews ◽

Martina Düfer ◽

Gisela Drews

Keyword(s):

Membrane Potential ◽

B Cells ◽

Intracellular Calcium ◽

Mitochondrial Membrane Potential ◽

Mitochondrial Membrane ◽

Calcium Activity ◽

Pancreatic B Cells

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Effects of l-leucine, its 2-keto acid metabolite and its nonmetabolized analogue on rat tumoral islet cell function

Journal of Molecular Endocrinology ◽

10.1677/jme.0.0010069 ◽

1988 ◽

Vol 1 (1) ◽

pp. 69-76 ◽

Cited By ~ 3

Author(s):

V. Leclercq-Meyer ◽

J. Marchand ◽

A. Sener ◽

F. Blachier ◽

W. J. Malaisse

Keyword(s):

Insulin Release ◽

Cell Function ◽

Islet Cells ◽

Adenine Nucleotides ◽

Secretory Response ◽

Acid Metabolite ◽

Dual Effect ◽

Islet Cell Function ◽

Insulinoma Cells ◽

Stimulation Of

ABSTRACT l-Leucine and 2-ketoisocaproate stimulated insulin release from perifused rat tumoral islet cells (RINm5F line). The secretory response coincided with an increase in the intracellular ATP/ADP ratio, a stimulation of 45Ca outflow from cells perifused in the presence of extracellular Ca2+, and an increase in 32P efflux from cells prelabelled with radioactive orthophosphate. In contrast to d-glucose, however, l-leucine or 2-ketoisocaproate failed to decrease 86Rb outflow, to inhibit 45Ca outflow from cells perifused in the absence of Ca2+ and to enhance the labelling of inositol-containing phospholipids in cells exposed to myo-[2-3H]inositol. These findings suggest that d-glucose, l-leucine and 2-ketoisocaproate exert dissimilar effects on the subcellular distribution of adenine nucleotides and/or 86Rb. The nonmetabolized analogue of l-leucine, 2-aminobicyclo-[2.2.1]heptane-2-carboxylic acid (BCH), also caused an initial stimulation of insulin release and 32P efflux, but this was soon followed by a severe and irreversible inhibition of insulin output, associated with a permanent enhancement of 86Rb outflow. The dual ionic and secretory response to BCH is interpreted in the light of its dual effect on the catabolism of endogenous amino and fatty acids, and raises the view that BCH could be used to interfere with the function of insulinoma cells.

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Insulin release, cGMP, cAMP, and membrane potential in acetylcholine-stimulated islets.

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1978.235.5.e493 ◽

1978 ◽

Vol 235 (5) ◽

pp. E493 ◽

Cited By ~ 1

Author(s):

E Gagerman ◽

L A Idahl ◽

H P Meissner ◽

I B T�ljedal

Keyword(s):

Membrane Potential ◽

Cyclic Amp ◽

Insulin Release ◽

Cyclic Gmp ◽

Spike Activity ◽

Obvious Effect ◽

Ionic Fluxes ◽

Mouse Islets ◽

Silent State ◽

Esterase Inhibitor

Acetylcholine potentiated the glucose-induced insulin release from microdissected mouse islets of Langerhans but had no effect on basal insulin release. Significant potentiation was obtained with 0.1 micron acetylcholine in the presence of 10 micron eserine and with 1 micron or more acetylcholine in the absence of a choline esterase inhibitor. Carbamylcholine, too, potentiated insulin release. Potentiation was blocked by methylatropine, whereas methylatropine alone had no effect on insulin release. Acetylcholine or carbamylcholine (5-500 micron) had no obvious effect on cyclic GMP or cyclic AMP in the islets. In the presence of 11.1 mM D-glucose, the membrane potential of beta-cells oscillated slowly between a polarized silent state of -50 to -55 mV and a depolarized active state of -33 to -39 mV, at which a fast spike activity occurred. Acetylcholine made the potential stay at the plateau and induced a continuous spike activity pattern. Atropine inhibited the electrical effects of acetylcholine but not those of glucose alone. It is suggested that cholinergic potentiation of insulin release is mediated by changes of transmembrane ionic fluxes, probably without the intervention of cyclic GMP or cyclic AMP.

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