scholarly journals Calcium and pancreatic secretion. I. Subcellular distribution of calcium and magnesium in the exocrine pancreas of the guinea pig.

1975 ◽  
Vol 65 (1) ◽  
pp. 88-102 ◽  
Author(s):  
F Clemente ◽  
J Meldolesi
Keyword(s):  
Guinea Pig ◽  
Subcellular Distribution ◽  
Pancreatic Secretion ◽  
Exocrine Pancreas ◽  
Acinar Cells ◽  
Cell Fractionation ◽  
Zymogen Granules ◽  
Membrane Bound ◽  
Calcium And Magnesium

The distribution of calcium and magnesium has been studied in the acinar cells of the pancreas of the guinea pig. Most of the magnesium was found to be associated with the rough microsomes (probably bound to the ribosomes) and with the postmicrosomal supernate. In contrast, calcium was distributed among all the particulate fractions, primarily the mitochondria, microsomes (especially smooth surfaced), zymogen granules, and the plasmalemma, and was low in the postmicrosomal supernate. Most of the calcium recovered in the particulate fractions was found to be membrane bound. The highest concentrations were found in the membranes of the zymogen granules and in the plasmalemma. By means of control experiments using -45Ca as the tracer, it was established that a considerable redistribution of calcium occurs during homogenization and cell fractionation. At least some of the resulting artifacts were estimated quantitatively and the data were corrected accordingly. The biochemical results were confirmed with the cytochemical antimonate technique carried out on the tissue as well as on isolated fractions. The role of calcium associated with the zymogen granules and with their limiting membranes is discussed in relation to the architecture of the granule and to the functionality of the pancreatic juice.

scholarly journals Cell fractionation studies on the guinea pig pancreas. Redistribution of exocrine proteins during tissue homogenization.

1978 ◽  
Vol 78 (1) ◽  
pp. 110-130 ◽  
Author(s):  
G A Scheele ◽  
G E Palade ◽  
A M Tartakoff
Keyword(s):  
Guinea Pig ◽  
Intracellular Transport ◽  
Cell Fraction ◽  
Cell Fractionation ◽  
Zymogen Granules ◽  
Cell Compartments ◽  
Intracellular Compartments ◽  
Primary Location ◽  
Double Label

A double-label protocol was used to estimate the extent of leakage and relocation artifacts that affect exocrine pancreatic proteins in cell fractionation experiments. Guinea pig pancreatic lobules were pulsed in vitro with a mixture of 14C-amino acids to enable the lobules to produce and process endogenously labeled exocrine proteins. At the end of the pulse (10 min) or after an appropriate chase interval, the lobules were homogenized in 0.3 M sucrose to which a complete mixture of 3H-labeled exocrine pancreatic proteins was added as an exogenous tracer. The distribution of both labels was studied in each cell fraction of interest at the level of TCA-insoluble proteins and individual exocrine proteins resolved by using a two-dimensional gel system. Based on the premises that the exogenous and endogenous label behave identically during homogenization-fractionation and that all endogenously labeled exocrine proteins found in the postmicrosomal supernate come from intracellular compartments ruptured during tissue homogenization, a series of equations was derived to quantitate leakage and adsorption and to define the ratio of endogenous label still in its primary location to total label (primary location index or PLI) for each cell fraction. Leakage was found to be uniform for all exocrine proteins, but unequal in extent from different cell compartments (condensing vacuoles is greater than zymogen granules is greater than rough endoplasmic reticulum) ; it increased with exposure to shearing forces especially in the case of zymogen granules and condensing vacuoles, and was substantially reduced from rough microsomes by adding 10 mM KCl to the homogenization media. Relocation of exogenous label by adsorption to other subcellular components was extensive (approximately 55%), uneven (free polysomes is greater than rough microsomes is greater than smooth microsomes and zymogen granules), preferential (cationic proteins are massively adsorbed to ribosomes and membranes, resulting in a complementary enrichment of the post-microsomal supernate with anionic exocrine proteins), and reversible (with successive 50-100 mM KCl washes). After correction for adsorption and leakage, the kinetics of intracellular transport derived from cell fractionation data were found to be nearly identical to those obtained from quantitative autoradiographic studies.

Nonparallel secretion of GP-2 from exocrine pancreas implies luminal coupling between acinar and duct cells

1994 ◽  
Vol 267 (1) ◽  
pp. G40-G51 ◽  
Author(s):  
S. D. Freedman ◽  
K. Sakamoto ◽  
G. A. Scheele
Keyword(s):  
Exocrine Pancreas ◽  
Acinar Cells ◽  
Zymogen Granule ◽  
Zymogen Granules ◽  
Pancreatic Acini ◽  
Glycosyl Phosphatidylinositol ◽  
Cellular Processes ◽  
Rat Exocrine Pancreas

The in vivo and in vitro secretion of glycoprotein-2 (GP-2), a glycosyl phosphatidylinositol (GPI)-anchored protein from the rat exocrine pancreas, was characterized. GP-2 was secreted in a nonparallel manner compared with amylase, a marker of secretory enzymes. Attenuated GP-2 secretion correlated with hormones that stimulated exocytosis in acinar cells. Augmented GP-2 secretion correlated with hormones that stimulated fluid and bicarbonate secretion from ductal elements. Immunofluorescence studies identified an enriched pool of GP-2 tightly bound to the apical membranes of acinar cells in addition to zymogen granules. This non-zymogen granule pool appears to represent the source of GP-2 released from acinar cells in a nonparallel manner. With the use of dispersed pancreatic acini largely devoid of ductal elements, GP-2 release was found to be augmented by alkaline pH. Thus GP-2 secretion appears to be modulated by two discrete cellular processes: 1) delivery of prereleased GP-2 within zymogen granules to the ductal lumen by exocytic mechanisms and 2) enzymatic release of GPI-anchored GP-2 from the luminal membranes, a kinetic process that appears to be regulated by secretin- or carbachol-induced secretion of bicarbonate.

Receptor for calcitonin gene-related peptide: binding to exocrine pancreas mediates biological actions

1985 ◽  
Vol 249 (1) ◽  
pp. G147-G151 ◽  
Author(s):  
H. Seifert ◽  
P. Sawchenko ◽  
J. Chesnut ◽  
J. Rivier ◽  
W. Vale ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Islets Of Langerhans ◽  
Exocrine Pancreas ◽  
Acinar Cells ◽  
Calcitonin Gene Related Peptide ◽  
Pancreatic Acinar Cells ◽  
Binding Studies ◽  
Amylase Release ◽  
Related Peptide ◽  
Calcitonin Gene

In the present study we demonstrate by immunohistochemical techniques that calcitonin gene-related peptide (CGRP) is present in nerve terminals in the islets of Langerhans. Furthermore, binding studies with 125I-CGRP indicate that dispersed acini from guinea pig pancreas contain a single class of high-affinity binding sites for CGRP with an apparent dissociation constant of 18 nM. Vasoactive intestinal peptide (VIP), rat growth hormone-releasing factor (rGRF), cholecystokinin octapeptide (CCK-OP), and bombesin do not interact with these receptors. Interaction of CGRP with these receptors leads to release of amylase from the acinar cells. Amylase release is half maximal at 0.3 nM CGRP and maximal at 3 nM CGRP. Maximal amylase release with CGRP is one-third of that observed with VIP. CGRP-induced amylase release is dependent on theophylline in the incubation medium. CGRP potentiates the amylase release stimulated by bombesin and CCK-OP but has no effect on amylase release stimulated by VIP, rGRF, and natural glucagon. CGRP stimulates a 25% increase in basal cellular cAMP. These results indicate that guinea pig pancreatic acinar cells contain a novel receptor for CGRP and that interaction of CGRP with this receptor leads to digestive enzyme secretion through a cAMP-mediated pathway. The presence of CGRP in the islets of Langerhans suggests a pathway for CGRP to reach the exocrine pancreas through an insuloacinar portal system.

Role of calcium in exocrine pancreatic secretion. IV. Calcium movements in isolated acinar cells of rabbit pancreas

1978 ◽  
Vol 544 (2) ◽  
pp. 338-350 ◽  
Author(s):  
B.A.M. Renckens ◽  
J.J. Schrijen ◽  
H.G.P. Swarts ◽  
J.J.H.H.M. De Pont ◽  
S.L. Bonting
Keyword(s):  
Pancreatic Secretion ◽  
Acinar Cells ◽  
Exocrine Pancreatic Secretion ◽  
Rabbit Pancreas

scholarly journals Role of plasma-membrane-bound sialidase NEU3 in clathrin-mediated endocytosis

2015 ◽  
Vol 470 (1) ◽  
pp. 131-144 ◽  
Author(s):  
Macarena Rodriguez-Walker ◽  
Aldo A. Vilcaes ◽  
Eduardo Garbarino-Pico ◽  
José L. Daniotti
Keyword(s):  
Plasma Membrane ◽  
Subcellular Distribution ◽  
Cellular Functions ◽  
Coated Pits ◽  
Key Enzyme ◽  
Membrane Bound

Sialidase NEU3 is a key enzyme in the catabolism of gangliosides. We demonstrated that NEU3 impairs cargo internalization via clathrin-coated pits, affecting AP-2 subcellular distribution. This study delineates previously unidentified cellular functions of NEU3.

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.

Pancreatic secretion of lysosomal enzymes stimulated by intraduodenal instillation of a liquid meal in rabbits

1992 ◽  
Vol 83 (3) ◽  
pp. 277-280 ◽  
Author(s):  
T. Hirano ◽  
T. Manabe ◽  
A. K. Saluja ◽  
M. L. Steer
Keyword(s):  
Body Weight ◽  
Pancreatic Secretion ◽  
Cathepsin B ◽  
Lysosomal Enzymes ◽  
Secretory Granules ◽  
Acinar Cells ◽  
Amylase Secretion ◽  
Zymogen Granules ◽  
Liquid Meal ◽  
Gut Hormone

1. Studies have been performed to determine the effect of intraduodenal food on pancreatic secretion of lysosomal enzymes. 2. Intraduodenal instillation of a liquid meal (3 g/kg body weight; 15.3% protein, 19.7% fat, 59.7% carbohydrate) caused significant increases in pancreatic juice volume and pancreatic secretion of amylase and protein compared with basal values for 2 h after instillation in anaesthetized rabbits. 3. Intraduodenal instillation of a liquid meal also caused significant increases in pancreatic secretion of three lysosomal enzymes (cathepsin B, N-β-acetyl-galactosaminidase and N-acetyl-β-glucosaminidase) compared with basal values for 2 h after instillation. 4. In addition, there were significant correlations between cathepsin B secretion and amylase secretion (r = 0.7764, P<0.001) and between cathepsin B secretion and protein secretion (r = 0.6216, P<0.001), both in basal conditions and in response to the liquid meal. 5. These results are evidence for the localization of lysosomal enzymes in the secretory granules-zymogen granules in normal acinar cells, and also indicate that the pancreatic secretion of lysosomal enzymes is gut-hormone-regulated.

Biphasic secretory response of exocrine pancreas to feeding

1980 ◽  
Vol 238 (4) ◽  
pp. G332-G337 ◽  
Author(s):  
Z. Itoh ◽  
R. Honda ◽  
K. Hiwatashi
Keyword(s):  
Pancreatic Secretion ◽  
Exocrine Pancreas ◽  
Physiological Role ◽  
Secretory Response ◽  
Conscious Dogs ◽  
Bicarbonate Secretion ◽  
Secretory Pattern ◽  
Second Peak

By means of a newly developed device, secretory response of the exocrine pancreas to feeding was continuously recorded for 24 h in conscious dogs. It was then found that the postprandial secretory pattern of the pancreas was biphasic. The first peak of secretion, rich in enzymes, occurred 2.3 +/- 0.11 h after feeding and its secretory volume was 25.3 +/- 3.10 ml/h. After the first peak, pancreatic secretion decreased slightly, but started to increase again. At 10.8 +/- 0.31 h after feeding, the second peak of secretion occurred and this was 40.5 +/- 2.93 ml/h, significantly higher than the first peak secretion and the greatest in 1 day. The second peak secretion did not contain a higher concentration of enzymes, but was rich in bicarbonate. Approximately 16 h after feeding, pancreatic secretion returned to the basal level, which continued until the next meal. That water and bicarbonate secretion of the pancreas is the greatest at about the 11th postprandial h had never been reported before. The physiological role of the pancreatic secretion at that time is more likely to be related to the neutralization of acid entering from the stomach than to the digestion of food.

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