Regulation of [Ca2+]c oscillations by plasma membrane Ca2+ fluxes: a role for natriuretic peptides

2003 ◽  
Vol 31 (5) ◽  
pp. 934-938 ◽  
Author(s):  
A.K. Green ◽  
O. Zolle ◽  
A.W.M. Simpson
Keyword(s):  
Plasma Membrane ◽  
Natriuretic Peptides ◽  
Physiological Role ◽  
Rat Hepatocytes ◽  
Cell Types ◽  
Isolated Rat Hepatocytes ◽  
Hypothetical Mechanism ◽  
Different Cell Types ◽  
Ecv304 Cell ◽  
Isolated Rat

We have investigated the effects of natriuretic peptides on oscillations in [Ca2+]c (cytosolic free Ca2+ concentration) in two different cell types: freshly isolated rat hepatocytes and the ECV304 cell line. Our data, from both cell types, suggest that natriuretic peptides modulate the frequency of [Ca2+]c oscillations through alterations in plasma membrane Ca2+ fluxes. Here, we review evidence for a role for plasma membrane Ca2+ fluxes in the control of the frequency of [Ca2+]c oscillations. We describe a hypothetical mechanism through which this might be achieved. We propose a physiological role for regulated control of Ca2+ efflux in modulating [Ca2+]c oscillations.

Plasma membrane fluidity in isolated rat hepatocytes: A comparative study using DPH and TMA-DPH as fluorescent probes

1989 ◽  
Vol 4 (3) ◽  
pp. 221-227 ◽  
Author(s):  
ANTONIO BENEDETTI ◽  
GIANNA FERRETTI ◽  
GIOVANNA CURATOLA ◽  
EUGENIO BRUNELLI ◽  
ANNE MARIE JÉZÉQUEL ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Comparative Study ◽  
Membrane Fluidity ◽  
Fluorescent Probes ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Plasma Membrane Fluidity ◽  
Isolated Rat

Agonist-induced internalisation of the angiotensin II-binding sites from plasma membranes of isolated rat hepatocytes

1997 ◽  
Vol 152 (3) ◽  
pp. 407-412 ◽  
Author(s):  
M Montiel ◽  
M C Caro ◽  
E Jiménez
Keyword(s):  
Plasma Membrane ◽  
Angiotensin Ii ◽  
Binding Sites ◽  
Plasma Membranes ◽  
Binding Capacity ◽  
Rat Hepatocytes ◽  
Receptor Complex ◽  
Ang Ii ◽  
Isolated Rat Hepatocytes ◽  
Isolated Rat

Angiotensin II (Ang II) provokes rapid internalisation of its receptor from plasma membranes in isolated rat hepatocytes. After 10 min stimulation with Ang II, plasma membrane lost about 60% of its 125I-Ang II-binding capacity. Internalisation was blocked by phenylarsine oxide (PhAsO), whereas okadaic acid, which markedly reduced the sustained phase of calcium mobilization, did not have a preventive effect on Ang II–receptor complex sequestration. These data suggest that Ang II receptor internalisation is probably independent of a phosphorylation/dephosphorylation cycle of critical serine/threonine residues in the receptor molecule. To establish a relationship between sequestration of the Ang II receptor and the physical properties of the Ang II-binding sites, 125I-Ang II–receptor complex profiles were analysed by isoelectric focusing. In plasma membrane preparations two predominant Ang II-binding sites, migrating to pI 6·8 and 6·5 were found. After exposure to Ang II, cells lost 125I-Ang II-binding capacity to the Ang II–receptor complex migrating at pI 6·8 which was prevented in PhAsO-treated cells. Pretreatment of hepatocytes with okadaic acid did not modify Ang II–receptor complex profiles, indicating that the binding sites corresponding to pI 6·5 and pI 6·8 do not represent a phosphorylated and/or non-phosphorylated form of the Ang II receptor. The results show that the Ang II–receptor complex isoform at pI 6·8 represents a functional form of the type-1 Ang II receptor. Further studies are necessary to identify the Ang II-related nature of the binding sites corresponding to pI 6·5. Journal of Endocrinology (1997) 152, 407–412

scholarly journals Sugar uptake by fluid-phase pinocytosis and diffusion in isolated rat hepatocytes

1987 ◽  
Vol 243 (3) ◽  
pp. 655-660 ◽  
Author(s):  
P B Gordon ◽  
H Høyvik ◽  
P O Seglen
Keyword(s):  
Plasma Membrane ◽  
Fluid Phase ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Free Sugar ◽  
Sugar Uptake ◽  
Isolated Rat Hepatocytes ◽  
Fluid Phase Endocytosis ◽  
And Diffusion ◽  
Isolated Rat

Measurements of sugar pinocytosis (fluid-phase endocytosis of radiolabelled sucrose, lactose and raffinose) in freshly isolated rat hepatocytes are disturbed by sugar diffusing into the cells through plasma-membrane blebs. Non-pinocytic entry may be even more pronounced at 0 degrees C, and is a major contributor to ‘background’ radioactivity. By electrodisruption of the plasma membrane, a distinction can be made between pinocytotically sequestered sugar and free sugar that has entered the cytosol by diffusion. Pinocytosis proceeds at a rate of 2%/h (relative to the intracellular fluid volume), whereas the rate of sucrose entry by diffusion is more than twice as high. Three pinocytotic compartments are distinguishable in isolated hepatocytes: (1) a rapidly recycling compartment, which is completely destroyed by electrodisruption, and which may represent pinocytic channels continuous with the plasma membrane; (2) a non-recycling (or very slowly recycling) electrodisruption-resistant compartment, which allows accumulation of the lysosomally hydrolysable sugar lactose, and which therefore must represent non-lysosomal vacuoles (endosomes?); (3) a lysosomal compartment (non-recycling, electrodisruption-resistant), which accumulates raffinose and sucrose, but which hydrolyses lactose. The last two compartments can be partially resolved in metrizamide/sucrose density gradients by the use of different sugar probes.

scholarly journals Transport of d-fructose and d-galactose into isolated rat hepatocytes

1980 ◽  
Vol 192 (1) ◽  
pp. 373-375 ◽  
Author(s):  
J D Craik ◽  
K R Elliott
Keyword(s):  
Plasma Membrane ◽  
External Medium ◽  
Rat Hepatocytes ◽  
Sugar Concentration ◽  
Isolated Rat Hepatocytes ◽  
Free Cells ◽  
Isolated Rat

Transport of D-fructose and D-galactose across the plasma membrane of isolated rat hepatocytes was followed for the net entry of sugars into sugar-free cells at 20 degrees C. Initial rates of transport showed a Michaelis-Menten dependency on sugar concentration, and transport was inhibited by 3-O-methyl-D-glucose in the external medium.

scholarly journals Metabolism of exogenous S-adenosylmethionine in isolated rat hepatocyte suspensions: methylation of plasma-membrane phospholipids without intracellular uptake

1997 ◽  
Vol 327 (2) ◽  
pp. 383-389 ◽  
Author(s):  
Fran¸oise BONTEMPS ◽  
Georges VAN DEN BERGHE
Keyword(s):  
Plasma Membrane ◽  
Animal Models ◽  
Rat Hepatocytes ◽  
Intracellular Uptake ◽  
Membrane Phospholipids ◽  
Rat Hepatocyte ◽  
Isolated Rat Hepatocytes ◽  
Liver Disorders ◽  
Slight Elevation ◽  
Isolated Rat

Administration of S-adenosylmethionine (AdoMet), the main biological methyl donor, has been shown to exert favourable effects on liver disorders in man and animal models. The mechanism of action of AdoMet has, however, remained elusive, mainly owing to controversies with respect to its capacity to enter intact liver cells. Incubation of isolated rat hepatocytes with 2 or 50 μM [methyl-14C]AdoMet showed that it was utilized predominantly to methylate cellular phospholipids, forming mainly phosphatidylcholine, although less than 0.2% of labelled AdoMet was found inside the cells. The concentration of neither AdoMet nor S-adenosylhomocysteine (AdoHcy), its demethylation product, was significantly elevated inside the cells. A slight elevation of intracellular AdoMet was only recorded on incubation with concentrations of AdoMet above 200 μM. AdoHcy, which does not penetrate cells, inhibited phospholipid methylation from [methyl-14C]AdoMet but not from [methyl-14C]Met. Elevation of intracellular AdoHcy by adenosine dialdehyde, an inhibitor of AdoHcy hydrolase, inhibited phospholipid methylation from [methyl-14C]Met, but virtually not at all from [methyl-14C]AdoMet. Taken together, these data indicate that exogenous AdoMet does not penetrate hepatocytes significantly but is utilized for phospholipid methylation on the outer surface of the plasma membrane.

Water and nonelectrolyte permeability of isolated rat hepatocytes

1986 ◽  
Vol 251 (6) ◽  
pp. C872-C882 ◽  
Author(s):  
G. Alpini ◽  
R. A. Garrick ◽  
M. J. Jones ◽  
R. Nunes ◽  
N. Tavoloni
Keyword(s):  
Plasma Membrane ◽  
Homogeneous Medium ◽  
Rat Hepatocytes ◽  
Bile Canaliculus ◽  
Isolated Rat Hepatocytes ◽  
Permeability Coefficients ◽  
Diffusive Permeability ◽  
Intracellular Medium ◽  
Tracer Molecules ◽  
Isolated Rat

We have measured the diffusive permeability coefficients of isolated rat hepatocytes to 3H2O, [14C]urea, [14C]erythritol, [14C]mannitol, [3H]sucrose, and [3H]inulin, employing a technique previously developed for erythrocytes (Redwood et al., J. Gen. Physiol 64:706-729, 1974). Diffusion coefficients for the tracer molecules were measured in packed hepatocytes, supernatant fluid, and intracellular medium (lysed hepatocytes) and were calculated assuming one-dimensional semi-infinite diffusion through a homogeneous medium. By applying the series-parallel pathway model, the following permeability coefficients (10(-5) cm/sec) for the hepatocyte plasma membrane were obtained. 3H2O, 98.6 +/- 18.4; [14C]urea, 18.2 +/- 5.3; [14C]erythritol, 4.8 +/- 1.6; [14C]mannitol, 3.1 +/- 1.4; [3H]sucrose, 0; [3H]inulin, 0. These results indicate that isolated rat hepatocytes are highly permeable to water and polar nonelectrolytes, when compared with other transporting epithelia. This relatively high cellular permeability is consistent with a model in which nonelectrolyte permeation is via an aqueous pathway of equivalent pore diameter of 8-12 A. The finding that [14C]erythritol and [14C]mannitol cross the hepatocyte plasma membrane indicates that these molecules enter the bile canaliculus through the transcellular route. Conversely, the failure of [3H]sucrose and [3H]inulin to permeate the hepatocyte in the isolated condition supports the concept that biliary entry of these large carbohydrates, at least that fraction which cannot be accounted for by a vesicular mechanism, must occur via the transjunctional shunt pathway.

Survival and Metabolic Function of Freshly Isolated Rat Hepatocytes Exposed First to a Heat Shock and Then to an Oxidative Stress

1999 ◽  
Vol 18 (4) ◽  
pp. 239-244
Author(s):  
Isabelle Latour ◽  
Pedro Buc-Calderon
Keyword(s):  
Oxidative Stress ◽  
Heat Shock ◽  
Reduced Glutathione ◽  
Rat Hepatocytes ◽  
Cell Types ◽  
Isolated Rat Hepatocytes ◽  
Tert Butyl Hydroperoxide ◽  
Shock Proteins ◽  
Freshly Isolated Rat Hepatocytes ◽  
Isolated Rat

The formation of heat shock proteins (hsp) leading to thermotolerance has been extensively reported in many cell types. In freshly isolated rat hepatocytes, hsp were synthesized after 60 minutes of incubation at 42°C. Cell survival was not modified by such a treatment, but protein synthesis, secretion of triglycerides as lipoproteins, and the maintenance of both ATP and glycogen levels were significantly impaired. When exposed to an oxidative stress, heat-shocked hepatocytes were not more resistant than cells always kept at 37°C. Conversely, the addition of tert-butyl hydroperoxide (tBOOH) resulted, in general, in an increased lactate dehydrogenase leakage. The metabolism of tBOOH, as estimated by the reduced glutathione (GSH) content and GSH peroxidase activity, was similar in both control and heat-shocked hepatocytes. Despite the synthesis of hsp in rat hepatocytes, the lack of resistance to a subsequent oxidant injury may be due to the metabolic impairment caused by the heat shock.

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