Regulation of pancreatic acinar cell insulin receptors by insulin

1984 ◽  
Vol 247 (2) ◽  
pp. G155-G160 ◽  
Author(s):  
J. Mossner ◽  
C. D. Logsdon ◽  
I. D. Goldfine ◽  
J. A. Williams
Keyword(s):  
Acinar Cell ◽  
Insulin Receptors ◽  
Insulin Binding ◽  
Pancreatic Acinar Cell ◽  
Diabetic Mice ◽  
Pancreatic Acini ◽  
Endogenous Insulin ◽  
High Concentrations ◽  
Triton X

In vivo pancreatic acini from normal mice are exposed to very high concentrations of insulin. To determine whether insulin receptors in these acini are downregulated by this endogenous insulin, insulin receptors on acini from both normal and diabetic mice were studied. Isolated acini from normal mice, which have accompanying islets of Langerhans, were studied under conditions where endogenous insulin was minimized. These acini bound 50% less 125I-insulin than acini from mice made diabetic with streptozotocin. Computer analysis of competition-inhibition curves showed a decrease in the number of insulin receptors in acini from normal mice when compared with acini from diabetic mice; however, the IC50 (a measure of receptor affinity) remained unchanged at approximately 1 nM. To study further the regulation of acinar cell insulin receptors, acini from diabetic mice were placed in suspension culture for 24 h. Addition of 1 microM insulin during the culture period led to a 30% decrease in subsequent 125I-insulin binding; the presence or absence of either epidermal growth factor or carbachol was without effect on insulin binding. The decrease in binding induced by insulin resulted from a change in receptor number without an alteration of the IC50. Measurement of total acinar cell insulin receptors by solubilization of these acini in 1% Triton X-100 showed that this insulin-induced decrease was due to a change in the total number of cellular insulin receptors. The present study suggests, therefore, that insulin can regulate its own receptor on pancreatic acini and that in vivo insulin receptors in normal pancreatic cells are downregulated, presumably due to high ambient insulin concentrations.

scholarly journals Cerulein hyperstimulation decreases AMP-activated protein kinase levels at the site of maximal zymogen activation

2012 ◽  
Vol 303 (6) ◽  
pp. G723-G732 ◽  
Author(s):  
Christine A. Shugrue ◽  
Martine Alexandre ◽  
Alexander Diaz de Villalvilla ◽  
Thomas R. Kolodecik ◽  
Lawrence H. Young ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Acinar Cell ◽  
Digestive Enzyme ◽  
Pancreatic Acinar Cell ◽  
In Vivo Studies ◽  
Zymogen Activation ◽  
Pancreatic Acini ◽  
Compound C ◽  
Ampk Activity

The premature activation of digestive enzyme zymogens in the pancreatic acinar cell is an important initiating event in acute pancreatitis. We have previously demonstrated that vacuolar ATPase (vATPase) activity is required for zymogen activation. Adenosine monophosphate-activated protein kinase (AMPK) regulates vATPase function in kidney and epididymal clear cells. To determine whether AMPK could affect pancreatitis responses, its effects were first examined in a cellular model of pancreatitis, cerulein-hyperstimulated (100 nM) pancreatic acini. This treatment caused a prominent increase in trypsin and chymotrypsin activities. Pretreatment with AICAR or metformin (AMPK activators) or compound C (an AMPK inhibitor) reduced or increased cerulein-induced zymogen activation, respectively. The association of the vATPase E subunit with membranes, a marker of its activation, tended to be inversely related to AMPK activity (assessed by AICAR and compound C treatments). Cerulein treatment did not change AMPK (α and β) levels but did lead to an increase in its activation (phosphorylation of Thr172) and induced the time-dependent translocation of the enzyme to a Triton-insoluble compartment. Basal in vivo studies showed that AMPK was widely distributed between membrane and soluble fractions generated by differential centrifugation. After cerulein hyperstimulation, AMPK levels selectively decreased in fractions containing the highest levels of active zymogens. These studies suggest that AMPK activity has a protective role in the pancreatic acinar cell that inhibits zymogen activation in the basal state, and this AMPK effect is reduced during pancreatitis. Therapies that prevent the selective reduction of AMPK in compartments that support zymogen activation could reduce injury during pancreatitis.

scholarly journals Effects of increased intracellular cAMP on carbachol-stimulated zymogen activation, secretion, and injury in the pancreatic acinar cell

2005 ◽  
Vol 288 (2) ◽  
pp. G235-G243 ◽  
Author(s):  
A. Chaudhuri ◽  
T. R. Kolodecik ◽  
F. S. Gorelick
Keyword(s):  
Acinar Cell ◽  
Cell Injury ◽  
Lactic Dehydrogenase ◽  
Pancreatic Acinar Cell ◽  
Enzyme Secretion ◽  
Intracellular Camp ◽  
Zymogen Activation ◽  
Trypan Blue Exclusion ◽  
Pancreatic Acini ◽  
High Concentrations

A characteristic of acute pancreatitis is the premature activation and retention of enzymes within the pancreatic acinar cell. Because ligands linked to cAMP production may prevent some forms of pancreatitis, we evaluated the effects of increased intracellular cAMP in the rat pancreatic acinar cell. Specifically, this study examined the effects of the cholinergic agonist carbachol and agents that increase cAMP [secretin and 8-bromoadenosine 3′,5′-cyclic monophosphate (8-Br-cAMP)] on zymogen activation (trypsin and chymotrypsin), enzyme secretion, and cellular injury in isolated pancreatic acini. Although cAMP agonists affected the responses to physiological concentrations of carbachol (1 μM), their most prominent effects were observed with supraphysiological concentrations (1 mM). When secretin was added to 1 mM carbachol, there was a slight increase in zymogen activation, but no change in the secretion of amylase or chymotrypsin. Furthermore, coaddition of secretin increased parameters of cell injury (trypan blue exclusion, lactic dehydrogenase release, and morphological markers) compared with carbachol (1 mM) alone. Although directly increasing cellular cAMP by 8-Br-cAMP caused much greater zymogen activation than carbachol (1 mM) alone or with secretin, 8-Br-cAMP cotreatment reduced all parameters of injury to the level of unstimulated acini. Furthermore, 8-Br-cAMP dramatically enhanced the secretion of amylase and chymotrypsin from the acinar cell. This study demonstrates that increasing acinar cell cAMP can overcome the inhibition of enzyme secretion caused by high concentrations of carbachol and eliminate acinar cell injury.

Mechanisms of vanadium action: insulin-mimetic or insulin-enhancing agent?

2000 ◽  
Vol 78 (10) ◽  
pp. 829-847 ◽  
Author(s):  
Margaret C Cam ◽  
Roger W Brownsey ◽  
John H McNeill
Keyword(s):  
Lipid Metabolism ◽  
Metabolic Effects ◽  
Isolated Cells ◽  
Insulin Mimetic ◽  
Endogenous Insulin ◽  
Carbohydrate And Lipid Metabolism ◽  
Low Concentrations ◽  
Tissue Sensitivity ◽  
High Concentrations

The demonstration that the trace element vanadium has insulin-like properties in isolated cells and tissues and in vivo has generated considerable enthusiasm for its potential therapeutic value in human diabetes. However, the mechanisms by which vanadium induces its metabolic effects in vivo remain poorly understood, and whether vanadium directly mimics or rather enhances insulin effects is considered in this review. It is clear that vanadium treatment results in the correction of several diabetes-related abnormalities in carbohydrate and lipid metabolism, and in gene expression. However, many of these in vivo insulin-like effects can be ascribed to the reversal of defects that are secondary to hyperglycemia. The observations that the glucose-lowering effect of vanadium depends on the presence of endogenous insulin whereas metabolic homeostasis in control animals appears not to be affected, suggest that vanadium does not act completely independently in vivo, but augments tissue sensitivity to low levels of plasma insulin. Another crucial consideration is one of dose-dependency in that insulin-like effects of vanadium in isolated cells are often demonstrated at high concentrations that are not normally achieved by chronic treatment in vivo and may induce toxic side effects. In addition, vanadium appears to be selective for specific actions of insulin in some tissues while failing to influence others. As the intracellular active forms of vanadium are not precisely defined, the site(s) of action of vanadium in metabolic and signal transduction pathways is still unknown. In this review, we therefore examine the evidence for and against the concept that vanadium is truly an insulin-mimetic agent at low concentrations in vivo. In considering the effects of vanadium on carbohydrate and lipid metabolism, we conclude that vanadium acts not globally, but selectively and by enhancing, rather than by mimicking the effects of insulin in vivo.Key words: vanadium, insulin-mimetic, insulin-like, insulin-enhancing.

Insulin receptors on Xenopus laevis oocytes: effects of injection of ob/ob mouse liver mRNA

1991 ◽  
Vol 100 (1) ◽  
pp. 167-171
Author(s):  
D.A. Diss ◽  
B.D. Greenstein
Keyword(s):  
Xenopus Laevis ◽  
Binding Sites ◽  
Insulin Receptors ◽  
Insulin Binding ◽  
Cell Types ◽  
Follicle Cells ◽  
Vitelline Membrane ◽  
Xenopus Laevis Oocytes ◽  
Endogenous Insulin ◽  
Order Of Magnitude

We describe here conditions for the detection of insulin binding sites on Xenopus laevis oocytes. The binding of 125I-labelled insulin displayed sigmoidal behaviour, which is characteristic of the binding relationship between insulin and its receptor. Resolution of the resulting curvilinear Scatchard plot into two components revealed KD values of 8.86 × 10(−10) +/− 1.9 × 10(−10) and 5.32 × 10(−9) +/− 2.4 × 10(−9) M and n values of 9.7 × 10(7) +/− 0.4 × 10(7) and 3.3 × 10(8) +/− 0.5 × 10(8) binding sites per oocyte, respectively. The possibility cannot be excluded, however, that receptors for IGF-1 were also being detected. Also described are conditions for the rapid and efficient removal of all tissues surrounding the oocyte, including the vitelline membrane. We could not detect any specific 125I-labelled insulin binding to oocytes that had their follicle cells or vitelline membrane removed and this was not due to the enzymic treatment used in the process. Microinjection of oocytes without follicular layers did not result in the appearance of any detectable insulin binding sites, which were, however, observed if oocytes were first stripped of the vitelline membrane. We suggest that oocytes may possess endogenous insulin receptors on their surface in numbers of the same order of magnitude as those present on somatic cells. The removal of tissues surrounding the oocyte should facilitate studies aimed at determining functional interactions of the various cell types during oocyte development and for studying insulin receptors on the oocyte-follicular cell complex.

Characterization of receptors for VIP on pancreatic acinar cell plasma membranes using covalent cross-linking

1987 ◽  
Vol 252 (3) ◽  
pp. G404-G412 ◽  
Author(s):  
K. E. McArthur ◽  
C. L. Wood ◽  
M. S. O'Dorisio ◽  
Z. C. Zhou ◽  
J. D. Gardner ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Acinar Cell ◽  
Sodium Dodecyl ◽  
Pancreatic Acinar Cell ◽  
Cross Linking ◽  
Pancreatic Acini ◽  
Vip Receptors ◽  
High Affinity ◽  
Polypeptide Band ◽  
Vip Receptor

Vasoactive intestinal peptide (VIP) receptors on guinea pig pancreatic acini differ from those on all other tissues in containing a high-affinity VIP receptor and a low-affinity VIP receptor that has a high affinity for secretin. To characterize the molecular components of these receptors, 125I-VIP was covalently cross-linked to these receptors by four different cross-linking agents: disuccinimidyl suberate, ethylene glycol bis (succinimidyl succinate), dithiobis (succinimidylpropionate), and m-maleimidobenzoyl N-hydroxysuccinimide ester. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated a single major polypeptide band of Mr 45,000 and a minor polypeptide band of Mr 30,000 were cross-linked to 125I-VIP. Covalent cross-linking only occurred when a cross-linking agent was added, was inhibited by GTP, was inhibited by VIP receptor agonists or antagonists that interact with VIP receptors, and not by other pancreatic secretagogues that interact with different receptors. For inhibiting both cross-linking and binding of 125I-VIP to the major polypeptide Mr 45,000 and the minor polypeptide Mr 30,000 components, the relative potencies were VIP greater than helodermin greater than rat growth hormone releasing factor greater than peptide histidine isoleucine greater than secretin. The apparent molecular weight of the cross-linked polypeptides were unchanged by dithiothreitol. Thus the high-affinity VIP receptor on pancreatic acinar cell membranes consists of a single major polypeptide of Mr 45,000, and this polypeptide is not a subunit of a larger disulfide-linked structure. Furthermore, either the low-affinity VIP/secretin-preferring receptor was not covalently cross-linked under the experimental conditions or it consists of a major polypeptide with the same molecular weight as the high-affinity VIP receptor.

Crambene induces pancreatic acinar cell apoptosis via the activation of mitochondrial pathway

2006 ◽  
Vol 291 (1) ◽  
pp. G95-G101 ◽  
Author(s):  
Yang Cao ◽  
Sharmila Adhikari ◽  
Abel Damien Ang ◽  
Marie Véronique Clément ◽  
Matthew Wallig ◽  
...  
Keyword(s):  
Acinar Cell ◽  
Cell Apoptosis ◽  
Caspase 3 ◽  
Fas Ligand ◽  
Annexin V ◽  
Acinar Cells ◽  
Mitochondrial Pathway ◽  
Pancreatic Acinar Cell ◽  
Pancreatic Acinar Cells ◽  
Pancreatic Acini

We investigated the apoptotic pathway activated by crambene (1-cyano-2-hydroxy-3-butene), a plant nitrile, on pancreatic acinar cells. As evidenced by annexin V-FITC staining, crambene treatment for 3 h induced the apoptosis but not necrosis of pancreatic acini. Caspase-3, -8, and -9 activities in acini treated with crambene were significantly higher than in untreated acini. Treatment with caspase-3, -8, and -9 inhibitors inhibited annexin V staining, as well as caspase-3 activity, pointing to an important role of these caspases in crambene-induced acinar cell apoptosis. The mitochondrial membrane potential was collapsed, and cytochrome c was released from the mitochondria in crambene-treated acini. Neither TNF-α nor Fas ligand levels were changed in pancreatic acinar cells after crambene treatment. These results provide evidence for the induction of pancreatic acinar cell apoptosis in vitro by crambene and suggest the involvement of mitochondrial pathway in pancreatic acinar cell apoptosis.

scholarly journals Expression of Clusterin in Pancreatic Acinar Cell Injuries In Vivo and In Vitro

Pancreas ◽  
2001 ◽  
Vol 22 (2) ◽  
pp. 126-134 ◽  
Author(s):  
Min-Jue Xie ◽  
Yoshiharu Motoo ◽  
Shi-Bing Su ◽  
Norio Sawabu
Keyword(s):  
Acinar Cell ◽  
Pancreatic Acinar Cell

scholarly journals Insertion of isolated insulin receptors into placental membrane vesicles

1992 ◽  
Vol 281 (2) ◽  
pp. 425-430 ◽  
Author(s):  
K Christiansen ◽  
J Carlsen
Keyword(s):  
Plasma Membrane ◽  
Membrane Protein ◽  
Insulin Receptors ◽  
Membrane Vesicles ◽  
Insulin Binding ◽  
Scatchard Analysis ◽  
Plasma Membrane Vesicles ◽  
Intact Cells ◽  
Receptor Number ◽  
Triton X

Purified human insulin receptors were inserted into placental plasma-membrane vesicles by fusion of membranes with receptor-lysophosphatidylcholine micelles. Scatchard analysis of insulin binding showed that about 10-15% of the added receptors became inserted into the membrane. The receptor number could be increased about 3-fold, corresponding to approx. 5 pmol of receptor/mg of membrane protein. The receptors became firmly bound to the membrane, as they could not be removed by extensive wash. The insertion of exogenous receptors could be demonstrated by immunoblotting. The inserted insulin receptor had the same insulin-binding affinity as the isolated receptor and the endogenous receptor of the membrane. Insulin binding in the presence or absence of Triton X-100 revealed that more than 80% of the exogenous receptors had a right-side-out orientation. Function of the inserted receptors, as observed by insulin-stimulated autophosphorylation, could be demonstrated. About 80% of the added lysophospholipid, corresponding to approx. 160 nmol of lysophospholipid/mg of membrane protein, became integrated into the membrane and was partly metabolized to phospholipid and to non-esterified fatty acid. The method of insertion of isolated insulin receptors using the natural detergent, lysophospholipid, may be a method for insertion of receptors into intact cells, where the lysophospholipid, as in the plasma-membrane vesicles, will be acylated to phospholipid.

Insulinlike growth factors bind to specific receptors in isolated pancreatic acini

1984 ◽  
Vol 246 (1) ◽  
pp. G96-G99
Author(s):  
J. A. Williams ◽  
A. Bailey ◽  
R. Humbel ◽  
I. D. Goldfine
Keyword(s):  
Growth Factors ◽  
Cell Function ◽  
Sugar Transport ◽  
Insulin Binding ◽  
Pancreatic Acinar Cell ◽  
Pancreatic Acini ◽  
New Class ◽  
Igf I ◽  
Specific Receptors ◽  
Insulinlike Growth Factors

Recently we have demonstrated the existence of specific receptors for insulin on pancreatic acini. Employing 125I-labeled insulinlike growth factors (IGFs) and insulin, we report the existence of distinct receptors for IGF-I and IGF-II on mouse pancreatic acini. Insulin competes with 125I-IGF-I with 1,000-fold less potency. By contrast, insulin increases the binding of 125I-IGF-II to its receptor. IGF in turn inhibits 125I-insulin binding to its receptor but with 250-fold less potency. Thus, distinct receptors exist on acini for IGF-I, IGF-II, and insulin. Moreover, IGF, like insulin, stimulates sugar transport by acini. The mechanism of IGF stimulation may be similar to insulin, as the effect of maximal concentrations of the two peptides when added together is not additive. These results raise the possibility, therefore, that IGFs may be a new class of physiological regulators of pancreatic acinar cell function.

Multiple isoforms of the ryanodine receptor are expressed in rat pancreatic acinar cells

2000 ◽  
Vol 351 (1) ◽  
pp. 265-271 ◽  
Author(s):  
Timothy J. FITZSIMMONS ◽  
Ilya GUKOVSKY ◽  
James A. McROBERTS ◽  
Edward RODRIGUEZ ◽  
F. Anthony LAI ◽  
...  
Keyword(s):  
Western Blot ◽  
Ryanodine Receptor ◽  
Acinar Cell ◽  
Acinar Cells ◽  
Protein Band ◽  
Pancreatic Acinar Cell ◽  
Pancreatic Acinar Cells ◽  
Rt Pcr ◽  
Pancreatic Acini ◽  
Cell Functions

Regulation of cytosolic Ca2+ is important for a variety of cell functions. The ryanodine receptor (RyR) is a Ca2+ channel that conducts Ca2+ from internal pools to the cytoplasm. To demonstrate the presence of the RyR in the pancreatic acinar cell, we performed reverse transcriptase (RT)-PCR, Western blot, immunocytochemistry and microscopic Ca2+-release measurements on these cells. RT-PCR showed the presence of mRNA for RyR isoforms 1, 2 and 3 in both rat pancreas and dispersed pancreatic acini. Furthermore, mRNA expression for RyR isoforms 1 and 2 was demonstrated by RT-PCR in individual pancreatic acinar cells selected under the microscope. Western-blot analysis of acinar cell immunoprecipitates, using antibodies against RyR1 and RyR2, showed a high-molecular-mass (> 250kDa) protein band that was much less intense when immunoprecipitated in the presence of RyR peptide. Functionally, permeablized acinar cells stimulated with the RyR activator, palmitoyl-CoA, released Ca2+ from both basolateral and apical regions. These data show that pancreatic acinar cells express multiple isoforms of the RyR and that there are functional receptors throughout the cell.

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