Glucose-inducible hypertrophy and suppression of anion efflux in rat beta cells

Hypertrophy of beta cells from obese fa/fa rats is associated with increased sensitivity to basal glucose. Exposure to glucose in culture distorts insulin secretion more in beta cells from large than small islets from fa/fa rats. The aim of the present study is to investigate whether increased beta cell volume is associated with both glucose hypersensitivity and altered activity of the glucose-sensitive anion conductance. Beta cells from fa/fa rats had increased volume compared with those from lean rats after 24 h culture. Three-day exposure to 25 mM glucose in culture induced 10-15% hypertrophy in beta cells from lean rats and basal secretion from intact islets was increased tenfold. Estimates of ion channel activity were made from measurement of radiolabeled ion efflux. Taurine efflux, a marker of glucose-regulated anion channel activity, was reduced after high glucose exposure but no alterations in glucose-dependent K+ efflux were detected. The reverse hemolytic plaque assay was used to determine the contributions of the number of secreting cells (recruitment) versus secretion per cell in beta cells from enlarged (>250 microm diameter), intermediate (125-250 microm) and small (<125 microm) islets from lean and obese rats exposed to conditions mimicking hyperglycemia. After overnight culture, basal secretion was twofold greater from beta cells of large fa/fa islets compared with all other groups. Recruitment at low glucose was increased in all lean or fa/fa beta cells derived from >125 microm islets. When beta cells from small islets were exposed to supra-physiological glucose for 3 days, recruitment was increased at basal glucose and blunted at high glucose. Glucose exposure converts the recruitment profile of beta cells from small islets to resemble that of beta cells from large islets while inducing cellular hypertrophy and reduced anion conductance. However, hypertrophy alone did not predict functional characteristics of overnight-cultured beta cells from fa/fa rats.

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Curcumin inhibits high glucose oxidative stress and apoptosis in pancreatic beta cells via CHOP PCG-1a nbsp and pERK1 2

Frontiers in Bioscience ◽

10.2741/4887 ◽

2020 ◽

Vol 25 (11) ◽

pp. 1974-1984

Author(s):

Rongping Chen

Keyword(s):

Oxidative Stress ◽

Beta Cells ◽

High Glucose ◽

Pancreatic Beta Cells

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Neutral amino acid transporter ASCT2 displays substrate-induced Na+ exchange and a substrate-gated anion conductance

Biochemical Journal ◽

10.1042/bj3460705 ◽

2000 ◽

Vol 346 (3) ◽

pp. 705-710 ◽

Cited By ~ 58

Author(s):

Angelika BRÖER ◽

Carsten WAGNER ◽

Florian LANG ◽

Stefan BRÖER

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Anion Channel ◽

Amino Acid Transporter ◽

Neutral Amino Acid ◽

Xenopus Laevis Oocytes ◽

Anion Conductance ◽

Neutral Amino Acid Transporter ◽

Inward Currents ◽

Acid Transporter

The neutral amino acid transporter ASCT2 mediates electroneutral obligatory antiport but at the same time requires Na+ for its function. To elucidate the mechanism, ASCT2 was expressed in Xenopus laevis oocytes and transport was analysed by flux studies and two-electrode voltage clamp recordings. Flux studies with 22NaCl indicated that the uptake of one molecule of glutamine or alanine is accompanied by the uptake of four to seven Na+ ions. Similarly to the transport of amino acids, the Na+ uptake was mediated by an obligatory Na+ exchange mechanism that depended on the presence of amino acids but was not stoichiometrically coupled to the amino acid transport. Other cations could not replace Na+ in this transport mechanism. When NaCl was replaced by NaSCN in the transport buffer, the superfusion of oocytes with amino acid substrates resulted in large inward currents, indicating the presence of a substrate-gated anion channel in the ASCT2 transporter. The Km for glutamine derived from these experiments is in good agreement with the Km derived from flux studies; it varied between 40 and 90 μM at holding potentials of -60 and -20 mV respectively. The permeability of the substrate-gated anion conductance decreased in the order SCN- NO3- > I- > Cl- and also required the presence of Na+.

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Organ Cultures of Pancreases of Fetuses from Diabetic Rats: Effects of High-glucose Media upon the Granulation of the Beta Cells and upon the Insulin Content of the Media

Diabetes ◽

10.2337/diab.16.12.846 ◽

1967 ◽

Vol 16 (12) ◽

pp. 846-851 ◽

Cited By ~ 8

Author(s):

L. J. Wells ◽

A. Lazarow

Keyword(s):

Beta Cells ◽

High Glucose ◽

Diabetic Rats ◽

Insulin Content ◽

Organ Cultures ◽

The Media

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Analysis of anion channel activity in chondrocytes in vitro model of osteoarthritis

Osteoarthritis and Cartilage ◽

10.1016/j.joca.2018.02.226 ◽

2018 ◽

Vol 26 ◽

pp. S104

Author(s):

K. Kumagai ◽

F. Toyoda ◽

C. Staunton ◽

U. Sharif ◽

R. Lewis ◽

...

Keyword(s):

In Vitro Model ◽

Anion Channel ◽

Channel Activity ◽

Vitro Model

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PO270 GINSENOSIDE RG3 SUPPRESSES INTERMITTENT HIGH GLUCOSE-INDUCED APOPTOSIS AND IMPROVES INSULIN SECRETION IN INS-1 PANCREATIC BETA-CELLS

Diabetes Research and Clinical Practice ◽

10.1016/s0168-8227(14)70564-9 ◽

2014 ◽

Vol 106 ◽

pp. S187 ◽

Cited By ~ 1

Author(s):

Y.J. Kim ◽

S.M. Park ◽

E.J. Lee ◽

T.N. Kim ◽

M.J. Kwon ◽

...

Keyword(s):

Insulin Secretion ◽

Beta Cells ◽

High Glucose ◽

Pancreatic Beta Cells ◽

Ginsenoside Rg3 ◽

Intermittent High Glucose ◽

Induced Apoptosis

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Mutation of a single amino acid converts the human water channel aquaporin 5 into an anion channel

AJP Cell Physiology ◽

10.1152/ajpcell.00129.2013 ◽

2013 ◽

Vol 305 (6) ◽

pp. C663-C672 ◽

Cited By ~ 12

Author(s):

Xue Qin ◽

Walter F. Boron

Keyword(s):

Water Channel ◽

Anion Channel ◽

Single Amino Acid ◽

Side Chain ◽

Wild Type ◽

Aquaporin 5 ◽

Anion Conductance ◽

Electrode Voltage ◽

Microelectrode Measurements ◽

Positively Charged

Aquaporin 6 (AQP6) is unique among mammalian AQPs in being an anion channel with negligible water permeability. However, the point mutation Asn60Gly converts AQP6 from an anion channel into a water channel. In the present study of human AQP5, we mutated Leu51 (corresponding to residue 61 in AQP6), the side chain of which faces the central pore. We evaluated function in Xenopus oocytes by two-electrode voltage clamp, video measurements of osmotic H2O permeability ( Pf), microelectrode measurements of surface pH (pHS) to assess CO2 permeability, and surface biotinylation. We found that AQP5-L51R does not exhibit the H2O or CO2 permeability of the wild-type protein but instead has a novel p-chloromercuribenzene sulfonate (pCMBS)-sensitive current. The double mutant AQP5-L51R/C182S renders the conductance insensitive to pCMBS, demonstrating that the current is intrinsic to AQP5. AQP5-L51R has the anion permeability sequence I− > NO3− ≅ NO2− > Br− > Cl− > HCO3− > gluconate. Of the other L51 mutants, L51T (polar uncharged) and L51V (nonpolar) retain H2O and CO2 permeability and do not exhibit anion conductance. L51D and L51E (negatively charged) have no H2O or CO2 permeability. L51K (positively charged) has an intermediate H2O and CO2 permeability and anion conductance. L51H is unusual in having a relatively low CO2 permeability and anion conductance, but a moderate Pf. Thus, positively charged mutations of L51 can convert AQP5 from a H2O/CO2 channel into an anion channel. However, the paradoxical effect of L51H is consistent with the hypothesis that CO2, in part, takes a pathway different from H2O through AQP5.

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