scholarly journals Regulation of liver cell volume and proteolysis by glucagon and insulin

1991 ◽  
Vol 278 (3) ◽  
pp. 771-777 ◽  
Author(s):  
S Vom Dahl ◽  
C Hallbrucker ◽  
F Lang ◽  
W Gerok ◽  
D Häussinger
Keyword(s):  
Cell Volume ◽  
Liver Cell ◽  
Intracellular Water ◽  
Cell Swelling ◽  
Isolated Perfused Rat Liver ◽  
Cell Shrinkage ◽  
Glucagon And Insulin ◽  
Opposing Effects ◽  
Water Space

The effects of insulin and glucagon on liver cell volume and proteolysis were studied in isolated perfused rat liver. The rate of proteolysis was assessed as [3H]leucine release from single-pass-perfused livers from rats which had been prelabelled in vivo by intraperitoneal injection of [3H]leucine. The intracellular water space was determined from the wash-out profiles of simultaneously added [3H]inulin and [14C]urea. In normo-osmotic (305 mosM) control perfusions the intracellular water space was 548 +/- 10 microliters/g wet mass (n = 44) and was increased by 16.5 +/- 2.6% (n = 6), i.e. by 85 +/- 14 microliters/g, after hypoosmotic exposure (225 mosM). Glucagon (0.1 microM) decreased the intracellular water space by 17 +/- 4% (n = 4), whereas insulin (35 nM) increased the intracellular water space by 9.3 +/- 1.4% (n = 15). Also, in isolated rat hepatocyte suspensions insulin (100 nM) caused cell swelling by 10.7 +/- 1.8% (n = 16), which was fully reversed by glucagon. In perfused liver, insulin-induced cell swelling was accompanied by a hepatic net K+ uptake (4.5 +/- 0.2 mumol/g) and an inhibition of proteolysis by 21 +/- 2% (n = 12); further addition of glucagon led to a net K+ release of 3.8 +/- 0.2 mumol/g (n = 7) and fully reversed the insulin effects on both cell volume and proteolysis. Similarly, insulin-induced cell swelling and inhibition of proteolysis were completely antagonized by hyperosmotic (385 mosM) cell shrinkage. Furthermore, cell swelling and inhibition of proteolysis after hypo-osmotic exposure or amino acid addition were reversed by glucagon-induced cell shrinkage. There was a close relationship between the extent of cell swelling and the inhibition of proteolysis, regardless of whether cell volume was modified by insulin, glucagon or aniso-osmotic exposure. The data show that glucagon and insulin are potent modulators of liver cell volume, at least in part by alterations of cellular K+ balance, and that their opposing effects on hepatic proteolysis can largely be explained by opposing effects on cell volume. It is hypothesized that hormone-induced alterations of cell volume may represent an important, not yet recognized, mechanism mediating hormonal effects on metabolism.

scholarly journals Regulation of cell volume in the perfused rat liver by hormones

1991 ◽  
Vol 280 (1) ◽  
pp. 105-109 ◽  
Author(s):  
S vom Dahl ◽  
C Hallbrucker ◽  
F Lang ◽  
D Häussinger
Keyword(s):  
Cell Volume ◽  
Rat Liver ◽  
Liver Cell ◽  
Intracellular Water ◽  
Cell Swelling ◽  
Perfused Rat Liver ◽  
Hormone Action ◽  
Cell Shrinkage ◽  
Volume Changes ◽  
Water Space

The effect of hormones on cell volume was studied in isolated perfused rat liver by assessing the intracellular water space as the difference between a [3H]inulin- and a [14C]urea-accessible space. The intracellular water space (control value 559 +/- 7 microliters/g of liver; n = 88) increased on addition of insulin (35 nM) or phenylephrine (5 microM) by 12 or 8% respectively, whereas it decreased with cyclic AMP (cAMP; 50 microM), glucagon (100 nM) or adenosine (50 microM) by 9, 13 or 6% respectively. Both insulin and glucagon exerted half-maximal effects on cell volume and cellular K+ balance at hormone concentrations found physiologically in the portal vein. Adenosine-induced cell shrinkage was explained by a net K+ release from the liver. Phenylephrine (5 microM) led to cell swelling by about 8%, which was additive to insulin-induced swelling. Extracellular ATP (20 microM) induced cell shrinkage by about 6%; this was additive to adenosine-induced shrinkage. Vasopressin (15 nM) did not appreciably change cell volume, but induced marked cell shrinkage when glucagon or cAMP was present. Insulin- and phenylephrine-induced cell swelling was counteracted by cAMP. Hormone-induced changes of intracellular water space could sufficiently explain accompanying liver mass changes induced by glucagon, cAMP, adenosine or vasopressin, but not those by phenylephrine and extracellular ATP. The data show that liver cell volume is subject to hormonal regulation, in part owing to modification of cellular K+ balance. Glucagon- and insulin-induced cell volume changes occur already in the presence of physiological hormone concentrations. The effects of Ca2(+)-mobilizing hormones on cell volume are not uniform. In view of the recently established role of cell volume changes in modulating liver cell function, the present findings open a new perspective on the mechanisms of hormone action in liver, underlining our previous hypothesis that cell volume changes may represent a ‘second messenger’ of hormone action.

scholarly journals Cell volume and bile acid excretion

1992 ◽  
Vol 288 (2) ◽  
pp. 681-689 ◽  
Author(s):  
D Häussinger ◽  
C Hallbrucker ◽  
N Saha ◽  
F Lang ◽  
W Gerok
Keyword(s):  
Amino Acids ◽  
Cell Volume ◽  
Liver Cell ◽  
Bile Flow ◽  
Cell Swelling ◽  
Isolated Perfused Rat Liver ◽  
Cell Shrinkage ◽  
Volume Changes ◽  
Close Relationship ◽  
Stimulation Of

The interaction between cell volume and taurocholate excretion into bile was studied in isolated perfused rat liver. Cell swelling due to hypo-osmotic exposure, addition of amino acids or insulin stimulated taurocholate excretion into bile and bile flow, whereas hyperosmotic cell shrinkage inhibited these. These effects were explained by changes in Vmax of taurocholate excretion into bile: Vmax. increased from about 300 to 700 nmol/min per g after cell swelling by 12-15% caused by either hypo-osmotic exposure or addition of amino acids under normo-osmotic conditions. Steady-state taurocholate excretion into bile was not affected when the influent K+ concentration was increased from 6 to 46 mM or decreased to 1 mM with iso-osmoticity being maintained by corresponding changes in the influent Na+ concentration. Replacement of 40 mM-NaCl by 80 mM-sucrose decreased taurocholate excretion into bile by about 70%; subsequent hypo-osmotic exposure by omission of sucrose increased taurocholate excretion to 160%. Only minor, statistically insignificant, effects of aniso-osmotic cell volume changes on the appearance of bolus-injected horseradish peroxidase in bile were observed. Taurocholate (400 microM) exhibited a cholestatic effect during hyperosmotic cell shrinkage, but not during hypo-osmotic cell swelling. Both taurocholate and tauroursodeoxycholate increased liver cell volume. Tauroursodeoxycholate stimulated taurocholate (100 microM) excretion into bile. This stimulatory effect was strongly dependent on the extent of tauroursodeoxycholate-induced cell swelling. During continuous infusion of taurocholate (100 microM) further addition of tauroursodeoxycholate at concentrations of 20, 50 and 100 microM increased cell volume by 10, 8 and 2% respectively, in parallel with a stimulation of taurocholate excretion into bile by 29, 27 and 9% respectively. There was a close relationship between the extent of cell volume changes and taurocholate excretion into bile, regardless of whether cell volume was modified by tauroursodeoxycholate, amino acids or aniso-osmotic exposure. The data suggest that: (i) liver cell volume is one important factor determining bile flow and biliary taurocholate excretion; (ii) swelling-induced stimulation of taurocholate excretion into bile is probably not explained by alterations of the membrane potential; (iii) bile acids modulate liver cell volume; (iv) taurocholate-induced cholestasis may depend on cell volume; (v) stimulation of taurocholate excretion into bile by tauroursodeoxycholate can largely be explained by tauroursodeoxycholate-induced cell swelling.

scholarly journals Coordinate modulation of Na-K-2Cl cotransport and K-Cl cotransport by cell volume and chloride

2002 ◽  
Vol 283 (5) ◽  
pp. C1422-C1431 ◽  
Author(s):  
Christian Lytle ◽  
Thomas McManus
Keyword(s):  
Cell Volume ◽  
Cell Volume Regulation ◽  
Specific Effect ◽  
Feedback System ◽  
Major Effect ◽  
Cell Swelling ◽  
Cell Shrinkage ◽  
Set Point

Na-K-2Cl cotransporter (NKCC) and K-Cl cotransporter (KCC) play key roles in cell volume regulation and epithelial Cl− transport. Reductions in either cell volume or cytosolic Cl− concentration ([Cl−]i) stimulate a corrective uptake of KCl and water via NKCC, whereas cell swelling triggers KCl loss via KCC. The dependence of these transporters on volume and [Cl−]i was evaluated in model duck red blood cells. Replacement of [Cl−]i with methanesulfonate elevated the volume set point at which NKCC activates and KCC inactivates. The set point was insensitive to cytosolic ionic strength. Reducing [Cl−]i at a constant driving force for inward NKCC and outward KCC caused the cells to adopt the new set point volume. Phosphopeptide maps of NKCC indicated that activation by cell shrinkage or low [Cl−]iis associated with phosphorylation of a similar constellation of Ser/Thr sites. Like shrinkage, reduction of [Cl−]i accelerated NKCC phosphorylation after abrupt inhibition of the deactivating phosphatase with calyculin A in vivo, whereas [Cl−] had no specific effect on dephosphorylation in vitro. Our results indicate that NKCC and KCC are reciprocally regulated by a negative feedback system dually modulated by cell volume and [Cl−]. The major effect of Cl− on NKCC is exerted through the volume-sensitive kinase that phosphorylates the transport protein.

scholarly journals Effects of hydration state on the synthesis and secretion of triacylglycerol by isolated rat hepatocytes. Implications for the actions of insulin and glucagon on hepatic secretion

1995 ◽  
Vol 312 (1) ◽  
pp. 57-62 ◽  
Author(s):  
V A Zammit
Keyword(s):  
Water Content ◽  
Cell Volume ◽  
Rat Hepatocytes ◽  
Cell Swelling ◽  
Cell Water ◽  
Cell Shrinkage ◽  
Isolated Rat Hepatocytes ◽  
Acute Changes ◽  
Isolated Rat

The effects of hepatocyte volume on the secretion of triacylglycerol were studied in order to test the suggestion that increases in the portal concentrations of osmolyte amino acids and metal ions during the prandial/early-absorptive phase may be involved in mediating the acute changes in glycerolipid metabolism observed in vivo [Zammit (1995) Biochem Soc. Trans. 23, 506-511]. Incubation of isolated rat hepatocytes with hypo-osmotic medium or in the presence of glutamine (in the presence or absence of leucine), conditions which gave an increase in cell water content of between 8 and 27%, resulted in a decrease in the rate of [14C]triacylglycerol (TAG) secretion when [14C]palmitate was used as substrate. The inhibition was proportional to the increase in cell water content. At low exogenous palmitate concentration (0.05 mM), the inhibition of [14C]TAG secretion was accompanied by a marked shift in the incorporation of label from TAG to phospholipid. In the presence of 0.5 mM palmitate this effect was attenuated, and in the presence of 1 mM palmitate it was abolished. Increased cell volume associated with incubation of hepatocytes with glutamine (in the presence or absence of leucine) also resulted in a decrease in the fraction of newly labelled TAG that was secreted into the medium. Decreased cell volume, achieved by incubation of hepatocytes with hyperosmotic medium (sufficient to decrease cell water content by approx. 9%) decreased overall [14C]TAG secretion, but did not affect the amount of label that was incorporated into phospholipid as a fraction of that incorporated into total glycerolipids. Cell shrinkage, however, diminished the fraction of newly labelled [14C]TAG that was secreted. When intracellular TAG was prelabelled with [3H]glycerol, it was found that cell shrinkage markedly inhibited (preformed) [3H]TAG secretion, whereas cell swelling did not affect this route of TAG secretion. The data are discussed in terms of the possible action of changes in cell hydration at the different loci at which hepatocyte TAG secretion is controlled, with reference to previous observations that both insulin and glucagon are able to inhibit TAG secretion in cultured rat hepatocytes and HepG2 cells.

Regulation of cell function by the cellular hydration state

1994 ◽  
Vol 267 (3) ◽  
pp. E343-E355 ◽  
Author(s):  
D. Haussinger ◽  
F. Lang ◽  
W. Gerok
Keyword(s):  
Cell Volume ◽  
Cell Function ◽  
Narrow Range ◽  
Cell Swelling ◽  
Metabolic Function ◽  
Cell Shrinkage ◽  
Short Term ◽  
Hydration State ◽  
Per Se ◽  
And Oxidative Stress

Cellular hydration can change within minutes under the influence of hormones, nutrients, and oxidative stress. Such short-term modulation of cell volume within a narrow range acts per se as a potent signal which modifies cellular metabolism and gene expression. It appears that cell swelling and cell shrinkage lead to certain opposite patterns of cellular metabolic function. Apparently, hormones and amino acids can trigger those patterns simply by altering cell volume. Thus alterations of cellular hydration may represent another important mechanism for metabolic control and act as another second or third messenger linking cell function to hormonal and environmental alterations.

Volume-sensitive Ca influx and release from intracellular pools in gastric parietal cells

1992 ◽  
Vol 263 (3) ◽  
pp. C584-C589 ◽  
Author(s):  
P. A. Negulescu ◽  
B. Munck ◽  
T. E. Machen
Keyword(s):  
Image Processing ◽  
Cell Volume ◽  
Digital Image Processing ◽  
Parietal Cells ◽  
Cell Swelling ◽  
Cell Shrinkage ◽  
Gastric Glands ◽  
Intact Rabbit ◽  
Induced Changes ◽  
Gastric Parietal Cells

The effects of osmotically induced changes in cell volume on cytoplasmic free Ca (Cai) were studied in parietal cells from intact rabbit gastric glands using digital image processing of fura-2 fluorescence. In resting unstimulated cells, Cai was unaffected by either cell swelling or shrinking when osmolarity was varied between 200 and 400 mosM (isotonicity 290 mosM). However, when cells were swelled in a 165 mosM solution (55% tonicity), a biphasic Ca increased was observed. On average, Cai increased transiently from 80 to 218 nM before stabilizing at approximately 140 nM. The peak was due to release from intracellular pools because it was present in Ca-free solutions while the sustained elevation was dependent on external Ca. In carbachol-stimulated cells, Ca influx was most sensitive to cell shrinkage. For example, addition of 25 mM sucrose (108% tonicity) caused a 30% decrease in the sustained carbachol-stimulated Cai increase (plateau). In contrast, carbachol-stimulated cells were relatively insensitive to cell swelling, with a 30% decrease in tonicity causing only a 15% increase in the plateau. However, as in the unstimulated cells, extreme (55% tonicity) swelling caused additional increases in Cai levels. The carbachol-dependent effects of changes in cell volume on Cai could be mimicked by treating cells with thapsigargin, an inhibitor of Ca pumps of intracellular membranes that also has been shown to stimulate Ca entry. Thus, although extreme swelling conditions (55% tonicity) could elicit Cai increases in either the presence or absence of agonist, agonist was required to observe Cai decreases due to cell shrinkage.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Cell swelling increases bile flow and taurocholate excretion into bile in isolated perfused rat liver

1992 ◽  
Vol 281 (3) ◽  
pp. 593-595 ◽  
Author(s):  
C Hallbrucker ◽  
F Lang ◽  
W Gerok ◽  
D Häussinger
Keyword(s):  
Bile Acid ◽  
Amino Acid ◽  
Cell Volume ◽  
Rat Liver ◽  
Bile Flow ◽  
Cell Swelling ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Volume Changes ◽  
Close Relationship

The effects of aniso-osmotically and amino-acid-induced cell-volume changes on bile flow and biliary taurocholate excretion were studied in isolated perfused rat liver. With taurocholate (100 microM) in the influent perfusate, hypo-osmotic exposure (225 mosmol/l) increased taurocholate excretion into bile and bile flow by 42 and 27% respectively, whereas inhibition by 32 and 47% respectively was observed after hyperosmotic (385 mosmol/l) exposure. The effects of aniso-moticity on taurocholate excretion into bile was observed throughout aniso-osmotic exposure, even after completion of volume-regulatory ion fluxes and were fully reversible upon re-exposure to normo-osmotic media. Hypo-osmotic cell swelling (225 mosmol/l) increased the Vmax. of taurocholate translocation from the sinusoidal compartment into bile about 2-fold. Also, cell swelling induced by glutamine and glycine stimulated both bile flow and biliary taurocholate excretion. There was a close relationship between the aniso-osmotically and amino-acid-induced change of cell volume and taurocholate excretion into bile. The data suggest that liver cell volume plays an important role in regulating bile-acid-dependent bile flow and biliary taurocholate excretion.

Effects of osmotic stress on the activity of MAPKs and PDGFR-β-mediated signal transduction in NIH-3T3 fibroblasts

2008 ◽  
Vol 294 (4) ◽  
pp. C1046-C1055 ◽  
Author(s):  
M.-B. Nielsen ◽  
S. T. Christensen ◽  
E. K. Hoffmann
Keyword(s):  
Signal Transduction ◽  
Osmotic Stress ◽  
Cell Volume ◽  
Nuclear Translocation ◽  
Cell Swelling ◽  
Cell Shrinkage ◽  
Jnk Pathway ◽  
Mapk Activity ◽  
3T3 Fibroblasts ◽  
Nih 3T3

Signaling in cell proliferation, cell migration, and apoptosis is highly affected by osmotic stress and changes in cell volume, although the mechanisms underlying the significance of cell volume as a signal in cell growth and death are poorly understood. In this study, we used NIH-3T3 fibroblasts in a serum- and nutrient-free inorganic medium (300 mosM) to analyze the effects of osmotic stress on MAPK activity and PDGF receptor (PDGFR)-β-mediated signal transduction. We found that hypoosmolarity (cell swelling at 211 mosM) induced the phosphorylation and nuclear translocation of ERK1/2, most likely via a pathway independent of PDGFR-β and MEK1/2. Conversely, hyperosmolarity (cell shrinkage at 582 mosM) moved nuclear and phosphorylated ERK1/2 to the cytoplasm and induced the phosphorylation and nuclear translocation of p38 and phosphorylation of JNK1/2. In a series of parallel experiments, hypoosmolarity did not affect PDGF-BB-induced activation of PDGFR-β, whereas hyperosmolarity strongly inhibited ligand-dependent PDGFR-β activation as well as downstream mitogenic signal components of the receptor, including Akt and the MEK1/2-ERK1/2 pathway. Based on these results, we conclude that ligand-dependent activation of PDGFR-β and its downstream effectors Akt, MEK1/2, and ERK1/2 is strongly modulated (inhibited) by hyperosmotic cell shrinkage, whereas cell swelling does not seem to affect the activation of the receptor but rather to activate ERK1/2 via a different mechanism. It is thus likely that cell swelling via activation of ERK1/2 and cell shrinkage via activation of the p38 and JNK pathway and inhibition of the PDGFR signaling pathway may act as key players in the regulation of tissue homeostasis.

scholarly journals WNK3 and WNK4 exhibit opposite sensitivity with respect to cell volume and intracellular chloride concentration

2020 ◽  
Vol 319 (2) ◽  
pp. C371-C380
Author(s):  
Diana Pacheco-Alvarez ◽  
Diego Luis Carrillo-Pérez ◽  
Adriana Mercado ◽  
Karla Leyva-Ríos ◽  
Erika Moreno ◽  
...  
Keyword(s):  
Cell Volume ◽  
Chloride Concentration ◽  
Cell Swelling ◽  
Cell Shrinkage ◽  
Serine Threonine Kinase ◽  
Intracellular Chloride ◽  
Highly Sensitive ◽  
A Cell ◽  
Carboxy Terminal ◽  
Intracellular Chloride Concentration

Cation-coupled chloride cotransporters (CCC) play a role in modulating intracellular chloride concentration ([Cl−]i) and cell volume. Cell shrinkage and cell swelling are accompanied by an increase or decrease in [Cl−]i, respectively. Cell shrinkage and a decrease in [Cl−]i increase the activity of NKCCs (Na-K-Cl cotransporters: NKCC1, NKCC2, and Na-Cl) and inhibit the activity of KCCs (K-Cl cotransporters: KCC1 to KCC4), wheras cell swelling and an increase in [Cl−]i activate KCCs and inhibit NKCCs; thus, it is unlikely that the same kinase is responsible for both effects. WNK1 and WNK4 are chloride-sensitive kinases that modulate the activity of CCC in response to changes in [Cl−]i. Here, we showed that WNK3, another member of the serine-threonine kinase WNK family with known effects on CCC, is not sensitive to [Cl−]i but can be regulated by changes in extracellular tonicity. In contrast, WNK4 is highly sensitive to [Cl−]i but is not regulated by changes in cell volume. The activity of WNK3 toward NaCl cotransporter is not affected by eliminating the chloride-binding site of WNK3, further confirming that the kinase is not sensitive to chloride. Chimeric WNK3/WNK4 proteins were produced, and analysis of the chimeras suggests that sequences within the WNK’s carboxy-terminal end may modulate the chloride affinity. We propose that WNK3 is a cell volume-sensitive kinase that translates changes in cell volume into phosphorylation of CCC.

scholarly journals Characterization of the hypertonically induced tyrosine phosphorylation of erythrocyte band 3

1998 ◽  
Vol 335 (2) ◽  
pp. 305-311 ◽  
Author(s):  
Giampaolo MINETTI ◽  
Claudio SEPPI ◽  
Annarita CIANA ◽  
Cesare BALDUINI ◽  
Philip S. LOW ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Cell Volume ◽  
Tyrosine Phosphorylation ◽  
Tyrosine Phosphatase ◽  
Volume Effect ◽  
Band 3 ◽  
Membrane Curvature ◽  
Cell Shrinkage ◽  
Constitutively Active

Human erythrocyte band 3 becomes rapidly phosphorylated on tyrosine residues after exposure of erythrocytes to hypertonic conditions. The driving force for this phosphorylation reaction seems to be a decrease in cell volume, because (1) changes in band 3 phosphotyrosine content accurately track repeated changes in erythrocyte volume through several cycles of swelling and shrinking; (2) the level of band 3 phosphorylation is independent of the osmolyte employed but strongly sensitive to the magnitude of cell shrinkage; and (3) exposure of erythrocytes to hypertonic buffers under conditions in which intracellular osmolarity increases but volume does not change (nystatin-treated cells) does not promote an increase in tyrosine phosphorylation. We hypothesize that shrinkage-induced tyrosine phosphorylation results either from an excluded-volume effect, stemming from an increase in intracellular crowding, or from changes in membrane curvature that accompany the decrease in cell volume. Although the net phosphorylation state of band 3 is shown to be due to a delicate balance between a constitutively active tyrosine phosphatase and constitutively active tyrosine kinase, the increase in phosphorylation during cell shrinkage was demonstrated to derive specifically from an activation of the latter. Further, a peculiar inhibition pattern of the volume-sensitive erythrocyte tyrosine kinase that matched that of p72syk, a tyrosine kinase already known to associate with band 3 in vivo, suggested the involvement of this kinase in the volume-dependent response.

Sign in / Sign up

Export Citation Format

Share Document