scholarly journals Iodoacetamide-induced sensitization of the pancreatic β-cells to glucose stimulation

1973 ◽  
Vol 132 (4) ◽  
pp. 775-789 ◽  
Author(s):  
Bo Hellman ◽  
Lars-Åke Idahl ◽  
Åke Lernmark ◽  
Janove Sehlin ◽  
Inge-Bert Täljedal
Keyword(s):  
Insulin Release ◽  
Inhibitory Action ◽  
Glucose Oxidation ◽  
Short Pulse ◽  
Calcium Deficiency ◽  
Cell Plasma ◽  
Previous Hypothesis ◽  
Inhibition Of Glycolysis ◽  
Microdissected Pancreatic Islets ◽  
Stimulate Insulin Release

At a glucose concentration of 3mm or less, iodoacetamide had no effect on the release of insulin from microdissected pancreatic islets of ob/ob-mice. At higher glucose concentrations, iodoacetamide exerted both an initial stimulatory and a subsequent inhibitory action. When islets were perifused with 1mm-iodoacetamide and 17mm-glucose the inhibitory action predominated after about 15min of transient stimulation. With decreasing concentrations of iodoacetamide the stimulatory phase was gradually prolonged, and with 0.003–0.1mm-iodoacetamide stimulation only was observed for 75min. Prolonged stimulation was also noted after a short pulse of iodoacetamide. Similar responses to 0.1mm-iodoacetamide were observed with islets from normal mice. With islets from ob/ob-mice the effect of 0.1mm-iodoacetamide was reproduced with 0.1mm-iodoacetate, whereas 0.1mm-acetamide had no apparent effect. Iodoacetamide increased the Vmax. of glucose-stimulated insulin release without altering the apparent Km for glucose. Leucine, glibenclamide or theophylline could not replace glucose in this synergistic action with iodoacetamide. Iodoacetamide rather inhibited the insulin-releasing action of theophylline. Iodoacetamide-induced potentiation of the glucose-stimulated insulin release was rapidly and reversibly inhibited by mannoheptulose, adrenaline, or calcium deficiency. The potentiating effect on insulin release was not paralleled by effects on glucose oxidation or on islet fructose 1,6-diphosphate. However, the inhibitory action of iodoacetamide might be explained by inhibition of glycolysis as evidenced by an inhibition of glucose oxidation and a rise of fructose 1,6-diphosphate. The results support our previous hypothesis that thiol reagents can stimulate insulin release by acting on relatively superficial thiol groups in the β-cell plasma membrane. Glycolysis seems to be necessary in order for iodoacetamide to stimulate in this way.

scholarly journals Effects of organic mercurials on mammalian pancreatic β-cells. Insulin release, glucose transport, glucose oxidation, membrane permeability and ultrastructure

1972 ◽  
Vol 129 (2) ◽  
pp. 241-254 ◽  
Author(s):  
Gunnar D. Bloom ◽  
Bo Hellman ◽  
Lars-Åke Idahl ◽  
Åke Lernmark ◽  
Janove Sehlin ◽  
...  
Keyword(s):  
Membrane Permeability ◽  
Glucose Transport ◽  
Insulin Release ◽  
Glucose Oxidation ◽  
Sulphonic Acid ◽  
Β Cells ◽  
Β Cell ◽  
Cell Plasma ◽  
Organic Mercurials

The effects of p-chloromercuribenzoic acid and chloromercuribenzene-p-sulphonic acid on pancreatic islets were studied in vitro. Obese–hyperglycaemic mice were used as the source of microdissected islets containing more than 90% β-cells. p-Chloromercuribenzoic acid and chloromercuribenzene-p-sulphonic acid stimulated insulin release at concentrations of 0.01mm or above. This stimulation was significantly inhibited by the omission of Ca2+or the addition of adrenaline, diazoxide or 2,4-dinitrophenol. p-Chloromercuribenzoic acid or chloromercuribenzene-p-sulphonic acid did not interfere with the insulin-releasing ability of glucose. Micro-perifusion experiments revealed that the release of insulin in response to organic mercurial occurred almost instantaneously, was reversible, and was biphasic. The two mercurials inhibited glucose transport as well as glucose oxidation, and increased the mannitol and sucrose spaces of isolated islets. Compared with the effects on insulin release, those on glucose transport and membrane permeability were characterized by a longer latency and/or required higher concentrations of organic mercurial. Apart from a seemingly higher proportion of β-cells exhibiting certain degenerative features, in islets exposed to 0.1mm-chloromercuribenzene-p-sulphonic acid for 60min, no significant differences with respect to β-cell fine structure were noted between non-incubated islets and islets incubated with chloromercuribenzene-p-sulphonic acid or glucose or both. It is suggested that insulin release may be regulated by relatively superficial thiol groups in the β-cell plasma membrane.

scholarly journals Effects of a phorbol ester and clomiphene on protein phosphorylation and insulin secretion in rat pancreatic islets

1988 ◽  
Vol 249 (3) ◽  
pp. 825-830 ◽  
Author(s):  
S J Hughes ◽  
S J Ashcroft
Keyword(s):  
Insulin Release ◽  
Inhibitory Action ◽  
Glucose Oxidation ◽  
Subcellular Fractionation ◽  
Mean Value ◽  
Particulate Fraction ◽  
Dependent Manner ◽  
Phosphorylation State ◽  
Kinase C ◽  
Dose Dependent

The potentiation of glucose-stimulated insulin release induced by 100 nM-12-O-tetradecanoylphorbol 13-acetate (TPA) was inhibited by clomiphene, an inhibitor of protein kinase C (PK C), in a dose-dependent manner. Clomiphene at concentrations up to 50 microM had a modest inhibitory action (27%) on insulin release stimulated by 10 mM-glucose alone, but had no effect on the potentiation of insulin release induced by forskolin. Islet PK C activity, associated with a particulate fraction, was stimulated maximally by 100 nM-TPA. This stimulation was blocked by clomiphene in a dose-dependent manner, with 50% inhibition at 30 microM. Incubation of intact islets with TPA after preincubation with [32P]Pi and 10 mM-glucose to label intracellular ATP resulted primarily in enhanced phosphorylation of a 37 kDa protein (mean value, +/- S.E.M., 36,700 +/- 600 Da; n = 7). This increased phosphorylation was blocked by the simultaneous inclusion of clomiphene. Subcellular fractionation revealed the presence of the 37 kDa phosphoprotein in a 24,000 g particulate fraction of islet homogenates. Neither clomiphene nor TPA affected the rate of glucose oxidation by islets. These results show that the phosphorylation state of a 37 kDa membrane protein parallels the modulation of insulin release induced by TPA and clomiphene and support a role for PK C in the insulin-secretory mechanism.

scholarly journals The pancreatic β-cell recognition of insulin secretagogues. Effects of calcium and sodium on glucose metabolism and insulin release

1974 ◽  
Vol 138 (1) ◽  
pp. 33-45 ◽  
Author(s):  
Bo Hellman ◽  
Lars-Åke Idahl ◽  
Åke Lernmark ◽  
Janove Sehlin ◽  
Inge-Bert Täljedal
Keyword(s):  
Glucose Metabolism ◽  
Insulin Release ◽  
Glucose Oxidation ◽  
Metabolic Model ◽  
Medium Composition ◽  
Cell Recognition ◽  
Β Cell ◽  
Metabolic Block ◽  
Microdissected Pancreatic Islets ◽  
Stimulus Recognition

The transport and oxidation of glucose, the content of fructose 1,6-diphosphate, and the release of insulin were studied in microdissected pancreatic islets of ob/ob mice incubated in Krebs–Ringer bicarbonate medium. Under control conditions glucose oxidation and insulin release showed a similar dependence on glucose concentration with the steepest slope in the range 5–12mm. The omission of Ca2+, or the substitution of choline ions for Na+, or the addition of diazoxide had little if any effect on glucose transport. However, Ca2+ or Na+ deficiency as well as diazoxide (7-chloro-3-methyl-1,2,4-benzothiadiazine 1,1-dioxide) or ouabain partially inhibited glucose oxidation. These alterations of medium composition also increased the islet content of fructose 1,6-diphosphate, as did the addition of adrenaline. Phentolamine [2-N-(3-hydroxyphenyl)-p-toluidinomethyl-2-imidazoline] counteracted the effects of adrenaline and Ca2+ deficiency on islet fructose 1,6-diphosphate. After equilibration in Na+-deficient medium, the islets exhibited an increase in basal insulin release whereas the secretory response to glucose was inhibited. The inhibitory effects of Na+ deficiency on the secretory responses to different concentrations of glucose correlated with those on 14CO2 production. When islets were incubated with 17mm-glucose, the sudden replacement of Na+ by choline ions resulted in a marked but transient stimulation of insulin release that was not accompanied by a demonstrable increase of glucose oxidation. Galactose and 3-O-methylglucose had no effect on glucose oxidation or on insulin release. The results are consistent with a metabolic model of the β-cell recognition of glucose as insulin secretagogue and with the assumption that Ca2+ or Na+ deficiency, or the addition of adrenaline or diazoxide, inhibit insulin release at some step distal to stimulus recognition. In addition the results suggest that these conditions create a partial metabolic block of glycolysis in the β-cells. Hence the interrelationship between the processes of stimulus recognition and insulin discharge may involve a positive feedback of secretion on glucose metabolism.

scholarly journals Long-term effects of glucose on insulin release and glucose oxidation by mouse pancreatic islets maintained in tissue culture

1974 ◽  
Vol 140 (3) ◽  
pp. 377-382 ◽  
Author(s):  
Arne Andersson
Keyword(s):  
Tissue Culture ◽  
B Cells ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
High Glucose ◽  
Glucose Concentration ◽  
Glucose Oxidation ◽  
Extracellular Glucose Concentration ◽  
Extracellular Glucose ◽  
Mouse Pancreatic Islets

Rates of glucose oxidation and insulin release in response to a wide range of glucose concentrations were studied in short-term experiments in isolated mouse pancreatic islets maintained in tissue culture for 6 days at either a physiological glucose concentration (6.7mm) or at a high glucose concentration (28mm). The curves relating glucose oxidation or insulin release to the extracellular glucose concentration obtained with islets cultured in 6.7mm-glucose displayed a sigmoid shape similar to that observed for freshly isolated non-cultured islets. By contrast islets that had been cultured in 28mm-glucose showed a linear relationship between the rate of glucose oxidation and the extracellular glucose concentration up to about 8mm-glucose. The maximal oxidative rate was twice that of the non-cultured islets and the glucose concentration associated with the half-maximal rate considerably decreased. In islets cultured at 28mm-glucose there was only a small increase in the insulin release in response to glucose, probably due to a depletion of stored insulin in those B cells that had been cultured in a high-glucose medium. It is concluded that exposure of B cells for 6 days to a glucose concentration comparable with that found in diabetic individuals causes adaptive metabolic alterations rather than degeneration of these cells.

Sensitivity to Cd2+ but resistance to Ni2+ of Ca2+ inflow into rat pancreatic islets

1990 ◽  
Vol 258 (3) ◽  
pp. E529-E533 ◽  
Author(s):  
P. O. Plasman ◽  
M. Hermann ◽  
A. Herchuelz ◽  
P. Lebrun
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Islet Cells ◽  
Excitable Cells ◽  
45Ca Uptake ◽  
Rat Pancreatic Islets ◽  
Cell Plasma ◽  
Different Types ◽  
45Ca Efflux ◽  
Ca2 Channels

The presence of different types [long lasting (L) and transient (T)] of active voltage-operated Ca2+ channels in islet cells was investigated by comparing the effects of Cd2+, Ni2+, and 1,4-dihydropyridines on 45Ca uptake, 45Ca efflux, and insulin release in intact rat pancreatic islets. In several other excitable cells the L-channel has been shown to be modulated by 1,4-dihydropyridines and Cd2+, whereas the T-channel was reported to be sensitive to Ni2+. Nifedipine and Cd2+ inhibited whereas BAY K 8644 enhanced the glucose (11.1, 22.2 mM)-stimulated short-term 45Ca uptake, 45Ca efflux, and insulin release. In contrast, the stimulatory effects of glucose (11.1, 22.2 mM) on 45Ca uptake, 45Ca efflux, and insulin release were unaffected by Ni2+. These findings confirm that glucose provokes Ca2+ entry mainly by activating voltage-sensitive Ca2+ channels of the L-type and suggest that the B-cell plasma membrane is not equipped with active T-type Ca2+ channels.

scholarly journals Effect of perchlorate on calcium uptake and insulin secretion in mouse pancreatic islets

1987 ◽  
Vol 248 (1) ◽  
pp. 109-115 ◽  
Author(s):  
J Sehlin
Keyword(s):  
Insulin Secretion ◽  
Beta Cell ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
Glucose Oxidation ◽  
Calcium Uptake ◽  
Maximum Effect ◽  
Mouse Pancreatic Islets ◽  
Stimulus Secretion Coupling ◽  
Ca2 Channels

Microdissected beta-cell-rich pancreatic islets of non-inbred ob/ob mice were used in studies of how perchlorate (CIO4-) affects stimulus-secretion coupling in beta-cells. CIO4- at 16 mM potentiated D-glucose-induced insulin release, without inducing secretion at non-stimulatory glucose concentrations. The potentiation mainly applied to the first phase of stimulated insulin release. In the presence of 20 mM-glucose, the half-maximum effect of CIO4- was reached at 5.5 mM and maximum effect at 12 mM of the anion. The potentiation was reversible and inhibitable by D-mannoheptulose (20 mM) or Ca2+ deficiency. CIO4- at 1-8 mM did not affect glucose oxidation. The effects on secretion were paralleled by a potentiation of glucose-induced 45Ca2+ influx during 3 min. K+-induced insulin secretion and 45Ca2+ uptake were potentiated by 8-16 mM-CIO4-. The spontaneous inactivation of K+-induced (20.9 mM-K+) insulin release was delayed by 8 mM-CIO4-. The anion potentiated the 45Ca2+ uptake induced by glibenclamide, which is known to depolarize the beta-cell. Insulin release was not affected by 1-10 mM-trichloroacetate. It is suggested that CIO4- stimulates the beta-cell by affecting the gating of voltage-controlled Ca2+ channels.

scholarly journals Abnormal glucose metabolism accompanies failure of glucose to stimulate insulin release from a rat pancreatic cell line (RINm5F)

1983 ◽  
Vol 212 (2) ◽  
pp. 439-443 ◽  
Author(s):  
P A Halban ◽  
G A Praz ◽  
C B Wollheim
Keyword(s):  
Glucose Metabolism ◽  
Cell Line ◽  
Insulin Release ◽  
Glucose Utilization ◽  
Rinm5f Cells ◽  
Pancreatic Cell ◽  
Abnormal Glucose Metabolism ◽  
Isolated Rat Islets ◽  
Stimulate Insulin Release ◽  
Stimulation Of

Glucose metabolism and insulin release were studied in isolated rat islets and in an insulin-producing rat cell-line (RINm5F). Intact islets displayed two components of glucose utilization, with glucose stimulation of insulin release being associated with the high-Km component (reflecting glucokinase-like activity). Glucose failed to stimulate insulin release from RINm5F cells, which only displayed a single low-Km component of glucose utilization. Only low-Km (hexokinase-like) glucose-phosphorylating activity was found for disrupted RINm5F cells. These changes in glucose metabolism may contribute towards the failure of glucose to stimulate insulin release from RINm5F cells.

P2 Receptor Agonists Stimulate Insulin Release from Human Pancreatic Islets

Pancreas ◽  
2001 ◽  
Vol 22 (1) ◽  
pp. 69-71 ◽  
Author(s):  
Josepha Fernandez-Alvarez ◽  
Dominique Hillaire-Buys ◽  
Marie-Madeleine Loubati??res-Mariani ◽  
Ramon Gomis ◽  
Pierre Petit
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
P2 Receptor ◽  
Human Pancreatic Islets ◽  
Receptor Agonists ◽  
Stimulate Insulin Release

Insulinotropic action of α-d-glucose pentaacetate: functional aspects

1997 ◽  
Vol 273 (6) ◽  
pp. E1090-E1101
Author(s):  
Willy J. Malaisse ◽  
Carmen Sánchez-Soto ◽  
M. Elena Larrieta ◽  
Marcia Hiriart ◽  
Hassan Jijakli ◽  
...  
Keyword(s):  
Ethyl Acetate ◽  
Insulin Release ◽  
Methyl Acetate ◽  
Cytochalasin B ◽  
Secretory Response ◽  
Coupling Mechanism ◽  
Functional Aspects ◽  
Acetate Methyl ◽  
Glucose Pentaacetate ◽  
Stimulate Insulin Release

The functional determinants of the insulinotropic action of α-d-glucose pentaacetate were investigated in rat pancreatic islets. The ester mimicked the effect of nutrient secretagogues by recruiting individual B cells into an active secretory state, stimulating proinsulin biosynthesis, inhibiting86Rb outflow, and augmenting45Ca efflux from prelabeled islets. The secretory response to the ester was suppressed in the absence of Ca2+ and potentiated by theophylline or cytochalasin B. The generation of acetate from the ester apparently played a small role in its insulinotropic action. Thus acetate, methyl acetate, ethyl acetate, α-d-galactose pentaacetate, and β-d-galactose pentaacetate all failed to stimulate insulin release. The secretory response to α-d-glucose pentaacetate was reproduced by β-d-glucose pentaacetate and, to a lesser extent, by β-l-glucose pentaacetate. It differed from that evoked by unesterifiedd-glucose by its resistance to 3- O-methyl-d-glucose,d-mannoheptulose, and 2-deoxy-d-glucose. It is concluded that the insulinotropic action of α-d-glucose pentaacetate, although linked to the generation of the hexose from its ester, entails a coupling mechanism that is not identical to that currently implied in the process of glucose-induced insulin release.

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