scholarly journals Accumulation of dopamine in mouse pancreatic B-cells following injection of L-DOPA. Localization to secretory granules and inhibition of insulin secretion

Diabetologia ◽  
1977 ◽  
Vol 13 (2) ◽  
pp. 117-124 ◽  
Author(s):  
L. E. Ericson ◽  
R. H�kanson ◽  
I. Lundquist
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
Secretory Granules ◽  
Pancreatic B Cells

scholarly journals Activation of alpha-2-adrenoceptors results in an increase in F-actin formation in HIT-T15 pancreatic B-cells

1995 ◽  
Vol 307 (1) ◽  
pp. 169-174 ◽  
Author(s):  
H C Cable ◽  
A el-Mansoury ◽  
N G Morgan
Keyword(s):  
Plasma Membrane ◽  
Insulin Secretion ◽  
B Cells ◽  
Fluorescence Microscopy ◽  
Pertussis Toxin ◽  
Actin Polymerization ◽  
Secretory Granules ◽  
Rhodamine Phalloidin ◽  
Late Step ◽  
Pancreatic B Cells

1. Alpha-2-adrenoceptor agonists, such as noradrenaline, are potent inhibitors of insulin secretion, and it has been suggested that they control a late step in the pathway of exocytosis. We have investigated whether this could be related to a change in the extent of actin polymerization in the pancreatic B-cell, since actin microfilaments are implicated in regulating the access of secretory granules to the plasma membrane prior to exocytosis. 2. Cultured HIT-T15 pancreatic B-cells responded to noradrenaline with an increase in F-actin content, as judged by a rise in the fluorescence output after probing of the cells with phalloidin (a toxin which binds specifically to F-actin) conjugated to rhodamine. The response to noradrenaline was rapid, dose-dependent and sustained and could be reproduced by the highly selective alpha-2-agonist UK14,304. Examination of HIT-T15 cells by fluorescence microscopy after treatment with rhodamine-phalloidin, revealed a significant localization of F-actin immediately adjacent to the plasma membrane. The pattern of F-actin distribution in the cells was not altered dramatically by noradrenaline, although the intensity of staining close to the plasma membrane appeared to be slightly reduced. 3. The increase in F-actin content induced by noradrenaline and UK14,304 was inhibited significantly by the alpha-2-antagonist idazoxan but not by the alpha-1-selective antagonist prazosin. Pretreatment of HIT-T15 cells with pertussis toxin did not lead to any direct alteration in F-actin content, although the toxin significantly modified the responses induced by noradrenaline and UK14,304. In each case, cells incubated for 24 h with pertussis toxin responded to the alpha-2-agonist with an enhanced fluorescence output, indicating that F-actin levels had increased still further. This did not correlate with any gross change in the distribution of F-actin as judged by fluorescence microscopy. 4. The results demonstrate that alpha-2-adrenoceptors are coupled to control of actin polymerization in HIT-T15 cells. They suggest that regulation of F-actin formation could be a component of the mechanism by which alpha-2-agonists mediate inhibition of insulin secretion.

Glucokinase in pancreatic B-cells and its inhibition by alloxan

1987 ◽  
Vol 115 (1) ◽  
pp. 21-29 ◽  
Author(s):  
Sigurd Lenzen ◽  
Markus Tiedge ◽  
Uwe Panten
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
B Cell ◽  
Metabolic Flux ◽  
Inhibitory Concentration ◽  
Pancreatic B Cell ◽  
High K ◽  
Pancreatic B Cells ◽  
Low K

Abstract. Characterization of glucokinase in pancreatic B-cells from ob/ob mice and from rat liver revealed identical characteristics. A narrow substrate specificity; high Km values for the two substrates, D-glucose and D-mannose, in the range of 10 and 20 mmol/l, respectively; higher Vmax values for D-glucose than for D-mannose; inhibition of glucokinase activities by D-mannoheptulose and by a specific glucokinase antibody. These characteristics distinguish glucokinase in soluble cytoplasmic fractions of pancreatic B-cells and liver from low Km hexokinases. Alloxan is a pancreatic B-cell cytotoxic agent, which has been widely used as a tool for the elucidation of the mechanisms of insulin secretion, because its inhibitory action on insulin secretion has been presumed to be intimately related to the mechanism of glucose-induced insulin secretion. Alloxan inhibited glucokinase but not hexokinase activity in cytoplasmic fractions of pancreatic B-cells and liver. The half maximal inhibitory concentration of alloxan was 5 μmol/l. Glucokinase activity was protected from alloxan toxicity only by D-glucose and D-mannose; the α anomer of D-glucose provided significantly greater protection than the β anomer. The non-metabolizable sugar 3-0-methyl-D-glucose did not provide protection of glucokinase activity against inhibition by alloxan. Thus, inhibition of pancreatic B-cell glucokinase may contribute to the inhibition of glucose-induced insulin secretion by alloxan. These results support the contention that glucokinase regulates the metabolic flux rate through the glycolytic chain in the pancreatic B-cell and thereby generates the signal for glucose-induced insulin secretion.

Glucokinase is concentrated in insulin-secretory granules of pancreatic B-cells

1999 ◽  
Vol 112 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Y. Toyoda ◽  
S. Yoshie ◽  
H. Shironoguchi ◽  
I. Miwa
Keyword(s):  
B Cells ◽  
Secretory Granules ◽  
Pancreatic B Cells

Fast insulin secretion reflects exocytosis of docked granules in mouse pancreatic B-cells

2002 ◽  
Vol 444 (1-2) ◽  
pp. 43-51 ◽  
Author(s):  
Charlotta S. Olofsson ◽  
Sven O. Göpel ◽  
Sebastian Barg ◽  
Juris Galvanovskis ◽  
Xiaosong Ma ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
Pancreatic B Cells ◽  
Fast Insulin

scholarly journals LOCALIZATION OF ACID PHOSPHATASE ACTIVITY AND SECRETION MECHANISM IN RABBIT PANCREATIC B-CELLS

1966 ◽  
Vol 14 (3) ◽  
pp. 233-246 ◽  
Author(s):  
SYDNEY S. LAZARUS ◽  
BRUNO W. VOLK ◽  
HERBERT BARDEN
Keyword(s):  
Acid Phosphatase ◽  
B Cells ◽  
B Cell ◽  
Phosphatase Activity ◽  
Acid Phosphatase Activity ◽  
Secretory Granules ◽  
Secretory Product ◽  
Cell Cytoplasm ◽  
Single Membrane ◽  
Pancreatic B Cells

Utilizing formaldehyde- or glutaraldehyde-fixed tissue and Gomori's lead method it was found by optical microscopy that rabbit pancreatic islet cell acid phosphatase activity is present in discrete, mostly perinuclear foci and that this distribution differs from that of the aldehyde fuchsin-positive secretory granules which are densely packed at the capillary pole of the cell. Electron microscopically lead reaction product was noted in dense bodies, as well as in structures thought to be Golgi vacuoles and vesicles, it was also present in the innermost of the Golgi cisternae, and at the periphery of adjacent single membrane-limited bodies whose origin can be traced from the proximal cisternae. These latter bodies in routinely prepared, osmium-fixed material show finely granular content, which is in contrast to the electron-dense, central body seen in secretory granules that appear to originate from endoplasmic reticulum. B-cell cytoplasm contained additional numerous, single membrane-limited vacuoles with pale content. These are thought also to represent secretion vacuoles but with insulin secretory product in a different physical or chemical state. The lack of acid phosphatase activity in B-cell secretion vacuoles, the dissimilarities in fine structure between the content of secretory elements and that of the Golgi-derived granular body, together with previous evidence that alteration in B-cell functional state does not result in altered number or distribution of acid phosphatase active elements in B-cell cytoplasm, indicate a lack of relationship between acid phosphatase and secretory granule formation or release in pancreatic B-cells. It is also hypothesized that the secretory vacuole with central dense granule may be a storage form while the pale vacuole is the one which liberates its content to the intercellular space.

scholarly journals Increase of gap junctions between pancreatic B-cells during stimulation of insulin secretion.

1979 ◽  
Vol 82 (2) ◽  
pp. 441-448 ◽  
Author(s):  
P Meda ◽  
A Perrelet ◽  
L Orci
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
Gap Junctions ◽  
Freeze Fracture ◽  
Secretory Activity ◽  
Isolated Rat Islets ◽  
Pancreatic B Cells ◽  
Stimulation Of

The development of gap junctions between pancreatic B-cells was quantitatively assessed in freeze-fracture replicas of isolated rat islets under different conditions of insulin secretion. The results show that in resting B-cells, gap junctions are small and scarce but that these junctions increase when insulin secretion is stimulated. Both a short (90 min) stimulation by glucose in vitro and a prolonged (2.5 d) stimulation by glibenclamide in vivo raise the number of gap junctions; in addition, the glibenclamide stimulation causes an increase in the size of individual gap junctions. As a consequence, the total area occupied by gap junctions on the B-cell membrane and the ratio of this area to the cell volume were found significantly increased in the latter condition. The slight increase of these values observed after the glucose stimulation did not reach significance. These data indicate a change of gap junctions during the secretory activity of the pancreatic B-cells. The possibility that the coupling of the cells is affected by the treatment is discussed.

Protein kinase C and the regulation of insulin secretion from pancreatic B cells

1991 ◽  
Vol 6 (2) ◽  
pp. 121-127 ◽  
Author(s):  
P. M. Jones ◽  
S. J. Persaud ◽  
S. L. Howell
Keyword(s):  
Protein Kinase C ◽  
Insulin Secretion ◽  
B Cells ◽  
Protein Kinase ◽  
Physiological Role ◽  
Cholinergic Agonists ◽  
Kinase C ◽  
Insulin Secretagogues ◽  
Pancreatic B Cells ◽  
Pkc Activation

ABSTRACT Protein kinase C (PKC) has been identified in islets of Langerhans and insulin-secreting tumour cells. Diacylglycerols (DAGs, the endogenous PKC activators) are generated in response to insulin secretagogues, although nutrient and non-nutrient secretagogues generate DAGs of different compositions and of different potencies as PKC activators. Exogenous activators of PKC stimulate insulin secretion from B cells, but attempts to define a physiological role for PKC by using inhibitors of this enzyme have produced ambiguous results. However, in studies using PKC-depleted B cells the loss of PKC activity does not inhibit glucose-induced insulin secretion, but markedly reduces responses to cholinergic agonists. These observations are supported by measurements of PKC activation which suggest that the enzyme is activated by cholinergic agonists, but not by nutrient secretagogues. Currently available experimental evidence therefore suggests that activation of PKC is not essential for nutrient-induced insulin secretion, but is required for the expression of a normal secretory response to cholinergic neurotransmitters.

scholarly journals Regulation of glucokinase and GLUT-2 glucose-transporter gene expression in pancreatic B-cells

1991 ◽  
Vol 279 (3) ◽  
pp. 899-901 ◽  
Author(s):  
M Tiedge ◽  
S Lenzen
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
B Cell ◽  
Glucose Transporter ◽  
Transcriptional Level ◽  
Signal Recognition ◽  
Transporter Gene ◽  
Physiological Regulation ◽  
Mrna Species ◽  
Pancreatic B Cells

Glucokinase (EC 2.7.1.2) is the signal-recognition enzyme in pancreatic B-cells for initiation of glucose-induced insulin secretion. We show here that both the glucokinase and glucose-transporter GLUT-2 genes are regulated physiologically. Fasting decreased B-cell glucokinase and glucose-transporter GLUT-2 mRNA in pancreatic B-cells as well as in liver, whereas refeeding induced expression of both genes. In pancreatic B-cells a approximately 4.4 kb glucokinase-related mRNA was detectable, in addition to the 2.8 kb form. This approximately 4.4 kb glucokinase transcript was drastically decreased during refeeding. The 2.8 kb mRNA, which is typical for pancreatic B-cells, was accompanied after refeeding by a 2.4 kb mRNA species typical for liver glucokinase. Starvation primarily decreased the 2.8 kb pancreatic B-cell glucokinase mRNA species. The concordant regulation of both genes may represent the basis for the physiological regulation of glucose-induced insulin secretion at a transcriptional level.

Effects of islet hormones on insulin secretion from cloned B cell lines, HIT-T15 and RINm5F

1989 ◽  
Vol 121 (3) ◽  
pp. 479-485 ◽  
Author(s):  
D. G. Lambert ◽  
T. W. Atkins
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
Insulin Release ◽  
Pancreatic Polypeptide ◽  
Islet Cell ◽  
Fine Tuning ◽  
Rinm5f Cells ◽  
Islet Hormones ◽  
Pancreatic B Cells ◽  
Islet Cell Hormones

ABSTRACT The effects of the islet cell hormones glucagon, somatostatin-28 and pancreatic polypeptide on insulin secretion from cultured cloned pancreatic B cells (HIT-T15 and RINm5F) have been investigated. Glucagon stimulates the secretion of insulin from HIT-T15 cells in the absence and presence of glucose and from RINm5F cells in the absence and presence of glyceraldehyde. HIT-T15 cells were more sensitive to the stimulatory effect of glucagon than RINm5F cells. Somatostatin-28 and pancreatic polypeptide, both alone and in combination, reduced glucose- and glucagon-stimulated insulin release from HIT-T15 cells and glyceraldehyde- and glucagon-stimulated insulin release from RINm5F cells. HIT-T15 cells were more sensitive to the inhibitory actions of somatostatin-28 and pancreatic polypeptide than RINm5F cells. This study supports the hypothesis that insulin release from normal B cells may be modified by the paracrine activity of islet hormones, glucagon, somatostatin and pancreatic polypeptide and probably occurs before any fine tuning imposed by subsequently released insulin. Journal of Endocrinology (1989) 121, 479–485

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