scholarly journals Regulation of actin polymerizaton in rat islets of Langerhans

1980 ◽  
Vol 192 (1) ◽  
pp. 381-383 ◽  
Author(s):  
S L Howell ◽  
M Tyhurst
Keyword(s):  
Insulin Secretion ◽  
Islets Of Langerhans ◽  
Subcellular Fractionation ◽  
Inhibition Assay ◽  
Rat Islets ◽  
Rat Islets Of Langerhans ◽  
Stimulation Of

A DNAase-inhibition assay was used to determine the proportions of globular (G-) and filamentous (F-) actin in islets of Langerhans after incubation in various conditions, or after subcellular fractionation. Stimulation of insulin secretion resulted in an ATP-dependent increase in the proportion of F-actin present; fractionation showed 80-90% of the actin to be present in the final supernatant.

scholarly journals Studies on the role of inositol trisphosphate in the regulation of insulin secretion from isolated rat islets of Langerhans

1985 ◽  
Vol 228 (3) ◽  
pp. 713-718 ◽  
Author(s):  
N G Morgan ◽  
G M Rumford ◽  
W Montague
Keyword(s):  
Insulin Secretion ◽  
Islets Of Langerhans ◽  
Islet Cells ◽  
Inositol Trisphosphate ◽  
Rat Islets ◽  
Isolated Rat Islets ◽  
Rat Islets Of Langerhans ◽  
Isolated Rat ◽  
Stimulation Of

Glucose (20 mM) and carbachol (1 mM) produced a rapid increase in [3H]inositol trisphosphate (InsP3) formation in isolated rat islets of Langerhans prelabelled with myo-[3H]inositol. The magnitude of the increase in InsP3 formation was similar when either agent was used alone and was additive when they were used together. In islets prelabelled with 45Ca2+ and treated with carbachol (1 mM), the rise in InsP3 correlated with a rapid, transient, release of 45Ca2+ from the cells, consistent with mobilization of 45Ca2+ from an intracellular pool. Under these conditions, however, insulin secretion was not increased. In contrast, islets prelabelled with 45Ca2+ and exposed to 20mM-glucose exhibited a delayed and decreased 45Ca2+ efflux, but released 7-8-fold more insulin than did those exposed to carbachol. Depletion of extracellular Ca2+ failed to modify the increase in InsP3 elicited by either glucose or carbachol, whereas it selectively inhibited the efflux of 45Ca2+ induced by glucose in preloaded islets. Under these conditions, however, glucose was still able to induce a small stimulation of the first phase of insulin secretion. These results demonstrate that polyphosphoinositide metabolism, Ca2+ mobilization and insulin release can all be dissociated in islet cells, and suggest that glucose and carbachol regulate these parameters by different mechanisms.

Stimulation of insulin secretion from isolated rat islets of Langerhans by melittin

1984 ◽  
Vol 4 (8) ◽  
pp. 665-671 ◽  
Author(s):  
Noel G. Morgan ◽  
William Montague
Keyword(s):  
Insulin Secretion ◽  
Islets Of Langerhans ◽  
Maximal Response ◽  
Secretory Rate ◽  
Rat Islets ◽  
Cell Plasma ◽  
Rat Islets Of Langerhans ◽  
Dose Dependent ◽  
Stimulation Of

Melittin, an amphipathic polypeptide, stimulated the secretion of insulin from rat islets of Langerhans incubated in vitro. The secretory response was dose-dependent and saturable with half the maximal response elicited by a melittin concentration of 4 μg/ml. The response was rapid in onset, an increase in secretion occurring within 2 rain of exposure of the islets to melittin (2 μg/ml). An enhanced secretory rate could be maintained for at least 40 rain in the presence of melittin but declined steadily when the agent was removed. Stimulation of secretion by melittin occurred in the absence of glucose and in the presence of both 4 mM and 8 mM glucose but not in the presence of 20 mM glucose. The effect of melittin on secretion was dependent on the presence of extracellular calcium but was not inhibited by norepinephrine. The data suggest that melittin may be a valuable agent for further study of the role played by the B-cell plasma membrane in the regulation of insulin secretion.

scholarly journals Stimulation of Adenylate Cyclase by Ca2+ and Calmodulin in Rat Islets of Langerhans: Explanation for the Glucose-induced Increase in Cyclic AMP Levels

Diabetes ◽  
1980 ◽  
Vol 29 (1) ◽  
pp. 74-77 ◽  
Author(s):  
G. W. G. Sharp ◽  
D. E. Wiedenkeller ◽  
D. Kaelin ◽  
E. G. Siegel ◽  
C. B. Wollheim
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Islets Of Langerhans ◽  
Rat Islets ◽  
Rat Islets Of Langerhans ◽  
Stimulation Of

Immunoprecipitation of a pertussis toxin substrate of the Go family from rat islets of Langerhans

1992 ◽  
Vol 12 (2) ◽  
pp. 95-100 ◽  
Author(s):  
Nicholas S. Berrow ◽  
Roger D. Hurst ◽  
Susan L. F. Chan ◽  
Noel G. Morgan
Keyword(s):  
Molecular Weight ◽  
Insulin Secretion ◽  
Adenylate Cyclase ◽  
G Protein ◽  
G Proteins ◽  
Islets Of Langerhans ◽  
Pertussis Toxin ◽  
Inhibitory Receptors ◽  
Rat Islets ◽  
Rat Islets Of Langerhans

Rat islets express a pertussis toxin sensitive G-protein involved in receptor-mediated inhibition of insulin secretion. This has been assumed previously to represent “Gi” which couples inhibitory receptors to adenylate cyclase. Incubation of islet G-proteins with32P-NAD and pertussis toxin resulted in the labelling of a band of molecular weight 40,000. This band was very broad and did not allow resolution of individual components. Incubation of the radiolabelled proteins with an anti-Go antiserum resulted in specific immunoprecipitation of a32P-labelled band. These results demonstrate that the complement of pertussis toxin sensitive G-proteins in rat islets includes Go.

Relationships between energy level and insulin secretion in isolated rat islets of langerhans

1992 ◽  
Vol 43 (8) ◽  
pp. 1859-1864 ◽  
Author(s):  
Mitsuaki Ohta ◽  
David Nelson ◽  
Jeanne M. Wilson ◽  
Martin D. Meglasson ◽  
Maria Erecińska
Keyword(s):  
Insulin Secretion ◽  
Energy Level ◽  
Islets Of Langerhans ◽  
Rat Islets ◽  
Isolated Rat Islets ◽  
Rat Islets Of Langerhans ◽  
Isolated Rat

scholarly journals Enhancement of glucagon secretion from isolated rat islets of Langerhans by phorbol 12-myristate 13-acetate

1986 ◽  
Vol 233 (1) ◽  
pp. 287-289 ◽  
Author(s):  
C S Hii ◽  
J Stutchfield ◽  
S L Howell
Keyword(s):  
Islets Of Langerhans ◽  
Glucagon Secretion ◽  
Glucose Stimulation ◽  
Rat Islets ◽  
Kinase C ◽  
Isolated Rat Islets ◽  
Rat Islets Of Langerhans ◽  
Isolated Rat ◽  
Stimulation Of

The phorbol ester 4 beta-phorbol 12-myristate 13-acetate (PMA), at concentrations of 0.1 microM and above, stimulated secretion of glucagon and of insulin from isolated rat islets of Langerhans incubated in the presence of 5.5 mM-glucose. Stimulation of secretion of both hormones by 1 microM-PMA persisted in the absence of external Ca2+, and could be abolished by incubating the islets at 4 degrees C. These findings suggest a role of protein kinase C in the alpha-cell (and beta-cell) secretory mechanism.

Arachidonic acid-induced insulin secretion from rat islets of Langerhans

1992 ◽  
Vol 8 (2) ◽  
pp. 95-101 ◽  
Author(s):  
A. M. Band ◽  
P. M. Jones ◽  
S. L. Howell
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Insulin Secretion ◽  
Incubation Temperature ◽  
Temperature Dependent ◽  
Rat Islets ◽  
Kinase C ◽  
The Media ◽  
Rat Islets Of Langerhans ◽  
Stimulation Of

ABSTRACT There is growing evidence that arachidonic acid (AA) and/or its metabolites may be involved in the control of insulin secretion. We have now investigated the effect of AA on insulin secretion from rat islets, and the possible involvement of protein kinase C (PKC) in this process. Exogenous AA stimulated insulin secretion from intact islets at a substimulatory concentration of glucose (2 mm), but did not further enhance glucose-induced (20 mm) insulin secretion. AA-induced insulin secretion was temperature dependent. The secretory responses seen at 37°C were totally abolished by reducing the incubation temperature to ≤34°C. AA-induced insulin secretion was not dependent upon extracellular Ca2+ and was potentiated by omission of Ca2+ or bovine serum albumin from the media. PKC in rat islets can thus be stimulated by AA, but the stimulation of PKC is not required for AA-induced insulin secretion.

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