scholarly journals Differential filipin labeling of the luminal membranes lining the pancreatic acinus.

1983 ◽  
Vol 31 (7) ◽  
pp. 952-955 ◽  
Author(s):  
L Orci ◽  
A Perrelet ◽  
R Montesano
Keyword(s):  
Acinar Cell ◽  
Exocrine Pancreas ◽  
Plasma Membranes ◽  
Basolateral Membrane ◽  
Acinar Cells ◽  
Pancreatic Acinus ◽  
Luminal Membrane

The cytochemical labeling of cholesterol by filipin in plasma membranes of the exocrine pancreas has shown a difference in the reactivity to filipin between the acinar and centro-acinar cells. The acinar cell has a poorly labeled luminal membrane but numerous filipin-cholesterol complexes on the basolateral membrane. In contrast, the centro-acinar cell shows a comparable degree of filipin labeling on both luminal and basolateral membrane. This difference in the distribution of filipin labeling suggests underlying differences in the organization of the respective membranes, probably related to their specific functions.

Regulation of electrolyte and fluid secretion in salivary acinar cells

1992 ◽  
Vol 263 (6) ◽  
pp. G823-G837 ◽  
Author(s):  
B. Nauntofte
Keyword(s):  
Ionic Composition ◽  
Basolateral Membrane ◽  
Acinar Cells ◽  
Fluid Secretion ◽  
Receptor Activation ◽  
Exchange Mechanism ◽  
Luminal Membrane ◽  
Net Uptake ◽  
Cl Channels ◽  
Simultaneous Activation

The primary secretion from exocrine gland cells is a fluid rich in Na+ and Cl- with a plasmalike ionic composition. Activation of specific receptors on the plasma membrane by hormones and neurotransmitters, which leads to activation of the phosphoinositol metabolism, results in release of Ca2+ from internal Ca2+ stores. Intracellular free Ca2+ concentration ([Ca2+]i) then rises simultaneously at both the basolateral and luminal parts of the acinar cell, reaching maximum values within 1 s after stimulation. In parotid acinar cells, increased [Ca2+]i activates the opening of maxi K+ channels located on the basolateral membrane and Cl- channels presumably located on the luminal membrane, resulting in rapid loss of K+ and Cl- and water and cell shrinkage. Extracellular electroneutrality is maintained by a paracellular Na+ flux into the lumen. Because of the simultaneous activation of K+ and Cl- channels, secretion occurs at a virtually constant membrane potential of about -60 mV. After maximal muscarinic cholinergic stimulation, loss of K+, Cl-, and water results in an approximate 25% reduction in cell volume within 10-15 s after receptor activation. Concomitant with loss of Cl-, there is a loss of HCO3- from the cell, causing a decrease in intracellular pH of 0.1 pH units because of the carbonic anhydrase-mediated conversion of CO2 into H+ and HCO3-. H+ generated from the metabolism and HCO3- production is compensated for by extrusion of H+ by a Na(+)-H+ exchange mechanism, which is responsible for approximately 75% of net Na+ gain that occurs after stimulation. Increased [Na+]i activates the Na(+)-K+ pump, which in turn extrudes Na+ from the cells. In both the unstimulated and stimulated states, cellular production of HCO3- can drive a net uptake of Cl- via the Cl(-)-HCO3- exchange mechanism operating in parallel with the Na(+)-H+ exchanger. The operation of the Cl(-)-HCO3- exchanger is, together with a Na(+)-K(+)-2Cl- cotransport system, essential for maintainance of a high [Cl-]i both in the unstimulated state and during Cl- reuptake.

scholarly journals Identification and localization of cholecystokinin-binding sites on rat pancreatic plasma membranes and acinar cells: a biochemical and autoradiographic study.

1983 ◽  
Vol 96 (5) ◽  
pp. 1288-1297 ◽  
Author(s):  
S A Rosenzweig ◽  
L J Miller ◽  
J D Jamieson
Keyword(s):  
Acinar Cell ◽  
Binding Sites ◽  
Plasma Membranes ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Cross Linking ◽  
Dependent Manner ◽  
Electron Microscopic ◽  
Electron Microscopic Autoradiography ◽  
Pancreatic Acini

Using the combined approaches of affinity labeling and light and electron microscopic autoradiography, we investigated the identification and localization of cholecystokinin (CCK)-binding sites on rat pancreatic acinar cells. To define the molecular properties of the CCK-binding site, we incubated rat pancreatic plasma membranes with 125-I-CCK-33 for 15 min at 23 degrees C followed by washing and cross-linking with disuccinimidyl suberate. Specific labeling of a major Mr 85,000 component was revealed as assessed by SDS PAGE under reducing conditions and autoradiography of the dried gels. Components of Mr greater than 200,000, Mr 130,000-140,000, and, Mr 55,000 were labeled under maximal cross-linking conditions. The labeling of all components was specifically inhibited by CCK-8 in a dose-dependent manner (Kd approximately 9 nM). The Mr 85,000 component had identical electrophoretic mobilities under reducing and nonreducing conditions indicating that it likely does not contain intramolecular disulfide bonds. The larger labeled species may be cross-linked oligomers of this binding protein or complexes between it and neighboring polypeptides. For studies on the distribution of CCK-binding sites, pancreatic acini were incubated with 125I-CCK-33 (0.1 nM) in the absence or presence of CCK-8 (1 microM) for 2 or 15 min at 37 degrees C, washed, and fixed in 2% glutaraldehyde. Quantitative autoradiographic analysis indicated that approximately 60% of the total grains were located within +/- 1 HD (1 HD = 100 nm) of the lateral and basal plasmalemma with little or no labeling of the apical plasmalemma. From these data, it was estimated that each acinar cell possesses at least 5,000-10,000 CCK-binding sites on its basolateral plasmalemma. The remaining grains showed no preferential concentration over the cytoplasm or nucleus. Together, these data indicate that CCK interacts with a Mr 85,000 protein located on the basolateral plasmalemma of the pancreatic acinar cell.

Extent and modulation of junctional communication between pancreatic acinar cells in vivo

1991 ◽  
Vol 261 (1) ◽  
pp. G28-G36 ◽  
Author(s):  
M. Chanson ◽  
L. Orci ◽  
P. Meda
Keyword(s):  
Acinar Cell ◽  
Exocrine Pancreas ◽  
Lucifer Yellow ◽  
Cell Communication ◽  
Acinar Cells ◽  
Pancreatic Acinar Cells ◽  
Cell Coupling ◽  
Junctional Communication ◽  
Physiological Relevance

To assess whether junctional communication may be of physiological relevance in the control of exocrine pancreas secretion, we have studied acinar cell coupling by microinjecting Lucifer Yellow CH in the intact pancreas of anesthetized rats. Reconstructions from serial sections showed that, under control conditions, pancreatic cells are extensively coupled within each acinus but do not communicate with centroacinar cells, duct cells, and cells of neighboring acini. Intravenous infusion of acetylcholine and caerulein, or electrical stimulation of the vagus nerve, increased pancreatic secretion (P less than 0.02-0.001). Under these stimulatory conditions, the extent of acinar cell communication was decreased (P less than 0.001) by 40%. The acetylcholine-induced uncoupling was prevented by treating rats with atropine. Thus, in the intact pancreas, acinar cells intercommunicate extensively within each acinus under resting conditions and reduce their coupling during stimulation. These data support the view that modulation of cell coupling is a physiologically relevant mechanism for the regulation of exocrine pancreas secretion in vivo.

ANF and exocrine pancreas: ultrastructural autoradiographic localization in acinar cells

1988 ◽  
Vol 254 (3) ◽  
pp. E301-E309 ◽  
Author(s):  
J. G. Chabot ◽  
G. Morel ◽  
M. Belles-Isles ◽  
L. Jeandel ◽  
S. Heisler
Keyword(s):  
Plasma Membrane ◽  
Golgi Apparatus ◽  
Binding Sites ◽  
Exocrine Pancreas ◽  
Plasma Membranes ◽  
Acinar Cells ◽  
Microscopic Level ◽  
Electron Microscopic Level ◽  
Zymogen Granules ◽  
Sites Of Action

Atrial natriuretic factor (ANF) binding sites have been recently demonstrated to be present in exocrine pancreas by an in vitro autoradiographic approach. An autoradiographic study was carried out to identify the exocrine cells containing ANF binding sites and to monitor the fate of 125I-labeled ANF in acinar cells after removal of pancreas at specific time intervals (1-30 min) after intravenous administration. At the light microscopic level, silver grains were found over acinar and centroacinar cells. Concomitant injection of an excess of unlabeled ANF inhibited the binding of labeled peptide by approximately 60%. At the electron microscopic level, the time-course study in acinar cells has revealed that of the cell compartments examined, plasma membrane, Golgi apparatus, mitochondria, and zymogen granules, the nucleus had distinct labeling patterns. Plasma membrane was maximally labeled 1 and 2 min after injection with 125I-ANF. Golgi apparatus was significantly labeled from 2 to 30 min after injection, mitochondria from 1 to 30 min after injection, zymogen granules at 1 and 15 min, and the nucleus only at 30 min. The lysosomal compartment was not labeled during the 30-min observation period. These results suggest that after binding to the plasma membrane, ANF is rapidly internalized and distributed to the intracellular organelles as a function of time. Labeling of the zymogen granules suggests that they may bind ANF and that the atrial peptide may be secreted by acinar cells. The significance of association of radioactivity with mitochondria and nuclei remains to be elucidated but may represent intracellular sites of action of ANF complementary to those on plasma membranes.

Calcium-activated potassium channels and fluid secretion by exocrine glands

1986 ◽  
Vol 251 (1) ◽  
pp. G1-G13 ◽  
Author(s):  
O. H. Petersen
Keyword(s):  
Single Channel ◽  
Basolateral Membrane ◽  
Acinar Cells ◽  
Fluid Secretion ◽  
Exocrine Glands ◽  
K Channels ◽  
Luminal Membrane ◽  
Channel Opening ◽  
Cell Current ◽  
Cl Channels

Fluid secretion by exocrine glands is regulated by neurotransmitters and hormones. The secretagogues act on the acinar cells by switching on two types of conductance pathways: K+-selective channels in the basolateral membrane and Cl(-)-selective channels localized to the luminal membrane. The K+ channels have been quantitatively characterized in patch-clamp single-channel and whole-cell current-recording studies. Opening of the K+ channels is determined by the membrane potential (depolarization enhances the probability of channel opening), and the intracellular free Ca2+ concentration ([Ca2+]i) (a rise in [Ca2+]i increases the open-state probability). The Cl- channels are also controlled by internal Ca2+ in such a way that an elevation of [Ca2+]i favors opening. Secretagogues evoking an increase in [Ca2+]i activate both sets of channels causing a substantial loss of cellular KCl. KCl is taken up via a Na+-K+-2Cl- cotransport mechanism in the basolateral membrane and the Na+ uptake activates the Na+-K+ pump. In the steady-state stimulated situation the three basolateral transport proteins, the K+ channels, the Na+-K+ pump, and the Na+-K+-2Cl- cotransporter operate together as an electrogenic Cl- pump. Cl- exits into the lumen via the Ca2+-activated Cl- channels and Na+ follows through the paracellular shunt pathway. When stimulation of the acinar cells ceases the K+ and Cl- conductance pathways close and the Na+-K+ pump together with the Na+-K+-2Cl- cotransporter operate as a KCl pump, restoring the intracellular KCl lost initially after start of stimulation and secretion stops.

scholarly journals Quantitative immunoelectron microscopic localization of (Na+,K+)ATPase in rat parotid gland.

1987 ◽  
Vol 35 (8) ◽  
pp. 871-879 ◽  
Author(s):  
T Iwano ◽  
M Akayama ◽  
A Yamamoto ◽  
K Omori ◽  
T Kumazawa ◽  
...  
Keyword(s):  
Parotid Gland ◽  
Plasma Membranes ◽  
Basolateral Membrane ◽  
Protein A ◽  
Acinar Cells ◽  
Gold Particles ◽  
Duct Cells ◽  
Rat Parotid Gland ◽  
Basal Plasma ◽  
Rat Parotid

Distribution of (Na+,K+)ATPase on the cell membranes of acinar and duct cells of rat parotid gland was investigated quantitatively by immunoelectron microscopy using the post-embedding protein A-gold technique. In acinar cells, ATPase was localized predominantly on the basolateral plasma membranes. A small but significant amount of (Na+,K+)ATPase was, however, detected on the luminal plasma membranes, especially on the microvillar region of the acinar cells; the surface density on the luminal membrane was approximately one third of that on the basolateral membranes. In duct cells, many gold particles were found on the basolateral membrane, especially along the basal infoldings of the plasma membranes, whereas no significant gold particles were found on the luminal plasma membranes, suggesting unilateral distribution of ATPase in duct cells. We suggest that in acinar cells sodium ion is not only transported paracellularly but is also actively transported intracellularly into the luminal space by the (Na+,K+)ATPase located on the luminal plasma membranes, and that water is passively transported to the luminal space to form a plasma-like isotonic primary saliva, while in the duct cells the same ion is selectively re-absorbed intracellularly by (Na+,K+)ATPase found in abundance along the many infoldings of the basal plasma membranes, thus producing the hypotonic saliva.

scholarly journals Kallikrein in rat pancreatic tissue after beta cell destruction or acinar cell atrophy.

1981 ◽  
Vol 29 (12) ◽  
pp. 1431-1436 ◽  
Author(s):  
T B Orstavik ◽  
I B Brekke ◽  
J Alumets ◽  
O A Carretero
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Acinar Cell ◽  
Pancreatic Beta Cells ◽  
Exocrine Pancreas ◽  
Acinar Cells ◽  
Beta Cell Destruction ◽  
Cell Destruction ◽  
Duct Occlusion ◽  
Cell Atrophy

The purpose of this study was to determine whether glandular kallikrein in rat pancreas is located in the beta cells of the endocrine pancreas or in the acinar cells of the exocrine pancreas. Kallikrein was measured by radial immunodiffusion and a direct radioimmunoassay in homogenates of pancreas obtained from 1) control rats, 2) rats with pancreatic beta cells selectively destroyed by streptozotocin, and 3) rats with acinar cell atrophy induced by pancreatic duct occlusion. Beta cell destruction was confirmed by the presence of hyperglycemia and by an almost total depletion of insulin-producing cells as demonstrated immunohistochemically. Acinar cell atrophy was confirmed histologically and by an almost total depletion of trypsin-like enzymes in pancreatic homogenates. The concentration of kallikrein in pancreatic homogenates was unchanged after beta cell destruction, whereas it was greatly decreased following acinar cell atrophy. Kallikrein was, by immunohistochemistry, demonstrated in the acinar cell only. The immunohistochemical localization of kallikrein agrees with the above results. These studies strongly indicate that kallikrein is predominantly located in the acinar cells of the exocrine pancreas.

Expression of the Na+-HCO3−cotransporter and its role in pHiregulation in guinea pig salivary glands

2006 ◽  
Vol 291 (6) ◽  
pp. G1031-G1040 ◽  
Author(s):  
Jingchao Li ◽  
Na-Youn Koo ◽  
Ik-Hyun Cho ◽  
Tae-Hwan Kwon ◽  
Se-Young Choi ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Parotid Gland ◽  
Salivary Glands ◽  
Submandibular Gland ◽  
Experimental Model ◽  
Basolateral Membrane ◽  
Acinar Cells ◽  
Underlying Mechanism ◽  
Rt Pcr ◽  
Luminal Membrane

Patterns of salivary HCO3−secretion vary and depend on species and gland types. However, the identities of the transporters involved in HCO3−transport and the underlying mechanism of intracellular pH (pHi) regulation in salivary glands still remain unclear. In this study, we examined the expression of the Na+-HCO3−cotransporter (NBC) and its role in pHiregulation in guinea pig salivary glands, which can serve as an experimental model to study HCO3−transport in human salivary glands. RT-PCR, immunohistochemistry, and pHimeasurements from BCECF-AM-loaded cells were performed. The amiloride-sensitive Na+/H+exchanger (NHE) played a putative role in pHiregulation in salivary acinar cells and also appeared to be involved in regulation in salivary ducts. In addition to NHE, NBC also played a role in pHiregulation in both acini and ducts. In the parotid gland, NBC1 was functionally expressed in the basolateral membrane (BLM) of acinar cells and the luminal membrane (LM) of ducts. In the submandibular gland, NBC1 was expressed only in the BLM of ducts. NBC1 expressed in these two types of salivary glands takes up HCO3−and is involved in pHiregulation. Although NBC3 immunoreactivity was also detected in submandibular gland acinar cells and in the ducts of both glands, it is unlikely that NBC3 plays any role in pHiregulation. We conclude that NBC1 is functionally expressed and plays a role in pHiregulation in guinea pig salivary glands but that its localization and role are different depending on the type of salivary glands.

TNF-α Suppresses Autophagic Flux in Acinar Cells in IgG4-Related Sialadenitis

2019 ◽  
Vol 98 (12) ◽  
pp. 1386-1396 ◽  
Author(s):  
X. Hong ◽  
S.N. Min ◽  
Y.Y. Zhang ◽  
Y.T. Lin ◽  
F. Wang ◽  
...  
Keyword(s):  
Acinar Cell ◽  
Cell Injury ◽  
Ex Vivo ◽  
Secretory Granules ◽  
Acinar Cells ◽  
Autophagic Flux ◽  
C6 Cells ◽  
Tnf Α ◽  
Α Level

IgG4-related sialadenitis (IgG4-RS) is a newly recognized immune-mediated systemic fibroinflammatory disease that affects salivary glands and leads to hyposalivation. Tumor necrosis factor–α (TNF-α) is a critical proinflammatory cytokine involved in several salivary gland disorders, but its role and mechanism regarding acinar cell injury in IgG4-RS are unknown. Here, we found that TNF-α level was significantly increased in serum and submandibular gland (SMG) of patients and that serum TNF-α level was negatively correlated with saliva flow rate. Ultrastructural observations of IgG4-RS SMGs revealed accumulation of large autophagic vacuoles, as well as dense fibrous bundles, decreased secretory granules, widened intercellular spaces, swollen mitochondria, and expanded endoplasmic reticulum. Expression levels of LC3 and p62 were both increased in patients’ SMGs. TNF-α treatment led to elevated levels of LC3II and p62 in both SMG-C6 cells and cultured human SMG tissues but did not further increase their levels when combined with bafilomycin A1 treatment. Moreover, transfection of Ad-mCherry-GFP-LC3B in SMG-C6 cells confirmed the suppression of autophagic flux after TNF-α treatment. Immunofluorescence imaging revealed that costaining of LC3 and the lysosomal marker LAMP2 was significantly decreased in patients, TNF-α–treated SMG-C6 cells, and cultured human SMGs, indicating a reduction in autophagosome-lysosome fusion. Furthermore, the ratio of pro/mature cathepsin D was elevated in vivo, ex vivo, and in vitro. TNF-α also appeared to induce abnormal acidification of lysosomes in acinar cells, as assessed by lysosomal pH and LysoTracker DND-26 fluorescence intensity. In addition, TNF-α treatment induced transcription factor EB (TFEB) redistribution in SMG-C6 cells, which was consistent with the changes observed in IgG4-RS patients. TNF-α increased the phosphorylation of extracellular signal–regulated kinase (ERK) 1/2, and inhibition of ERK1/2 by U0126 reversed TNF-α–induced TFEB redistribution, lysosomal dysfunction, and autophagic flux suppression. These findings suggest that TNF-α is a key cytokine related to acinar cell injury in IgG4-RS through ERK1/2-mediated autophagic flux suppression.

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