scholarly journals The microviscosity of liver plasma membranes of rats fed with oleoylanilide

1984 ◽  
Vol 218 (1) ◽  
pp. 125-129 ◽  
Author(s):  
R Pagani ◽  
M T Portoles ◽  
F G Gavilanes ◽  
P Garcia-Barreno ◽  
A M Municio
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Fluorescence Polarization ◽  
Plasma Membranes ◽  
Fluorescence Probe ◽  
Isolated Hepatocytes ◽  
Polarization Parameter ◽  
Lipid Interactions ◽  
Liver Plasma Membranes

Oleoylanilide was administered orally to groups of rats according to different patterns. Oleoylanilide was perfused at different concentrations through rat liver. Oleoylanilide was added to isolated hepatocytes. Oleoylanilide was added to plasma-membrane preparations. Membrane preparations were obtained after experiments performed in vivo and perfusion experiments and, by using 1,6-diphenylhexa-1,3,5-triene as fluorescence probe, the fluorescence polarization parameter was measured, from which the microviscosity (eta) was calculated. In all cases the microviscosity decreased markedly. Addition of oleoylanilide to hepatocyte preparations and to isolated membranes produced the same effect, increasing the fluidity of the membranes. These data suggest that oleoylanilide partitions into the membrane, disordering some lipid interactions.

scholarly journals Lysophosphatidylcholines can modulate the activity of the glucagon-stimulated adenylate cyclase from rat liver plasma membranes

1979 ◽  
Vol 178 (1) ◽  
pp. 217-221 ◽  
Author(s):  
M D Houslay ◽  
R W Palmer
Keyword(s):  
Adenylate Cyclase ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Hormone Receptors ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Liver Plasma Membranes ◽  
Rat Liver Plasma Membranes ◽  
Increased Sensitivity

1. Synthetic lysophosphatidylcholines inhibit the glucagon-stimulated adenylate cyclase activity of rat liver plasma membranes at concentrations two to five times lower than those needed to inhibit the fluoride-stimulated activity. 2. Specific 125I-labelled glucagon binding to hormone receptors is inhibited at concentrations similar to those inhibiting the fluoride-stimulated activity. 3. At concentrations of lysophosphatidylcholines immediately below those causing inhibition, an activation of adenylate cyclase activity or hormone binding was observed. 4 These effects are essentially reversible. 5. We conclude that the increased sensitivity of glucagon-stimulated adenylate cyclase to inhibition may be due to the lysophosphatidylcholines interfering with the physical coupling between the hormone receptor and catalytic unit of adenylate cyclase. 6. We suggest that, in vivo, it is possible that lysophosphatidylcholines may modulate the activity of adenylate cyclase only when it is in the hormone-stimulated state.

scholarly journals ISOLATION OF RAT LIVER PLASMA MEMBRANES

1970 ◽  
Vol 47 (3) ◽  
pp. 604-618 ◽  
Author(s):  
Oscar Touster ◽  
N. N. Aronson ◽  
John T. Dulaney ◽  
Herman Hendrickson
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Preparative Method ◽  
Membrane Localization ◽  
Plasma Membrane Localization ◽  
Liver Plasma Membranes ◽  
Nucleotide Pyrophosphatase ◽  
Rat Liver Plasma Membranes

Nucleotide pyrophosphatase and phosphodiesterase I of rat liver have been found to be localized primarily in cell particulates highly enriched with respect to the most commonly accepted plasma membrane marker, 5'-nucleotidase, and therefore should themselves be assigned a plasma membrane localization. The observation that plasma membranes sediment in isotonic sucrose with both nuclear and microsomal fractions was exploited to obtain plasma membrane preparations from each fraction. Both preparations are similar in chemical and enzymic composition. Moreover, the preparative method developed in this study appears to give the best combination of yield, purity, and reproducibility available. The question of the possible identity of nucleotide pyrophosphatase and phosphodiesterase I is considered, and evidence is presented suggesting that these activities may be manifestations of the same enzyme.

Incorporation in vivo of [32P]orthophosphate and [Me-3H]choline into rough microsomal, Golgi, and plasma membranes of rat liver

1977 ◽  
Vol 55 (8) ◽  
pp. 876-885 ◽  
Author(s):  
Patricia L. Chang ◽  
John R. Riordan ◽  
Mario A. Moscarello ◽  
Jennifer M. Sturgess
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Specific Activity ◽  
Specific Radioactivity ◽  
Marker Enzyme ◽  
Golgi Membranes ◽  
Endomembrane Flow

To study membrane biogenesis and to test the validity of the endomembrane flow hypothesis, incorporation of 32P and [Me-3H]choline in vivo into membranes of the rat liver was followed. Rough microsomal, Golgi-rich, and plasma membrane fractions were monitored with marker enzyme assays and shown with morphometric analysis to contain 82% rough microsomes, at least 70% Golgi complexes, and 88% plasma membranes, respectively. Membrane subfractions from the rough microsomal and Golgi-rich fractions were prepared by sonic disruption.At 5 to 30 min after 32P injection, the specific radioactivity of phosphatidylcholine was higher in the rough microsomal membranes than in the Golgi membranes. From 1 to 3 h, the specific activity of phosphatidylcholine in Golgi membranes became higher and reached the maximum at about 3 h. Although the plasma membrane had the lowest specific radioactivity throughout 0.25–3 h, it increased rapidly thereafter to attain the highest specific activity at 5 h. Both rough microsomal and plasma membranes reached their maxima at 5 h.The specific radioactivity of [32P]phosphatidylethanolamine in the three membrane fractions was similar to that of [32P]phosphatidylcholine except from 5 to 30 min, when the specific radioactivity of phosphatidylethanolamine in the Golgi membranes was similar to the rough microsomal membranes.At 15 min to 5 h after [Me-3H]choline injection, more than 90% of the radioactivity in all the membranes was acid-precipitable. The specific radioactivities of the acid-precipitated membranes, expressed as dpm per milligram protein, reached the maximum at 3 h. After [Me-3H]choline injection, the specific radioactivity of phosphatidylcholine separated from the lipid extract of the acid-precipitated membranes (dpm per micromole phosphorus) did not differ significantly in the three membrane fractions. The results indicated rapid incorporation of choline into membrane phosphatidylcholine by the rough endoplasmic reticulum, Golgi, and plasma membranes simultaneously.The data with both 32P and [Me-3H]choline precursors did not support the endomembrane flow hypothesis. The Golgi complexes apparently synthesized phosphatidylethanolamine and incorporated choline into phosphatidylcholine as well as the endoplasmic reticulum. The results are discussed with relevance to current hypotheses on the biogenesis and transfer of membrane phospholipids.

scholarly journals Lack of vasopressin receptors in liver, but not in kidney, of ob/ob mice

1983 ◽  
Vol 216 (2) ◽  
pp. 475-480 ◽  
Author(s):  
F Assimacopoulos-Jeannet ◽  
B Cantau ◽  
G van de Werve ◽  
S Jard ◽  
B Jeanrenaud
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Metabolic Response ◽  
Isolated Hepatocytes ◽  
The Other ◽  
Kidney Medulla ◽  
Liver Plasma Membrane ◽  
Liver Plasma Membranes ◽  
Vasopressin Receptors

The activity of phosphorylase a was measured in isolated hepatocytes from fed lean and ob/ob mice after addition of vasopressin, angiotensin, phenylephrine and glucagon. The binding of these hormones to purified liver plasma membranes was also determined. In hepatocytes of ob/ob mice, no increase in phosphorylase a was measured after addition of vasopressin, whereas the other hormones promoted an increase in the activity of the enzyme. No specific vasopressin receptors could be measured on purified liver plasma membrane of ob/ob mice. A decrease in the number of receptors for angiotensin and glucagon, without modification of the affinity, was also observed. No restoration of the number of vasopressin receptors was observed in liver of ob/ob mice starved for 3 days or in younger (5-6 weeks) animals. Vasopressin receptors and vasopressin-stimulated adenylate cyclase, measured on purified kidney medulla membranes, were similar in both lean and ob/ob mice. The data indicate a selective lack of vasopressin receptors and metabolic response in liver of the ob/ob mouse.

scholarly journals Alkaline ribonuclease and phosphodiesterase activity in rat liver plasma membranes

1973 ◽  
Vol 132 (3) ◽  
pp. 449-458 ◽  
Author(s):  
Terence D. Prospero ◽  
Malcolm L. E. Burge ◽  
Kenneth A. Norris ◽  
Richard H. Hinton ◽  
Eric Reid
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Gradient Centrifugation ◽  
Ribonuclease Activity ◽  
Nuclear Fraction ◽  
Phosphodiesterase Activity ◽  
Ph Optimum ◽  
Liver Plasma Membranes ◽  
Rat Liver Plasma Membranes

The ribonuclease and phosphodiesterase activities of rat liver plasma membranes, purified from the crude nuclear fraction by centrifugation in an A-XII zonal rotor and flotation, were examined and compared. The plasma membrane is responsible for between 65 and 90% of the phosphodiesterase activity of the cell and between 25 and 30% of the particulate ribonuclease activity measured at pH8.7 in the presence of 7.5mm-MgCl2. Both enzymes were most active between pH8.5 and 8.9. Close to the pH optimum, both enzymes were more active in Tris buffer than in Bicine or glycine buffer. Both plasma-membrane phosphodiesterase and ribonuclease were strongly activated by Mg2+, there being at least a 12-fold difference between the activity in the presence of Mg2+ and of EDTA. There is, however, a difference in the response of the enzymes to Mg2+ and EDTA in that the phosphodiesterase is fully activated by 1.0mm-MgCl2 and fully inhibited by 1.0mm-EDTA, whereas the ribonuclease requires 7.5mm-MgCl2 for full activation and 5mm-EDTA for full inhibition. Density-gradient centrifugation has indicated that on solubilization in Triton X-100 most of the ribonuclease activity is released into a small fragment of the same size as that containing the phosphodiesterase activity. The relationship between the two activities is discussed in view of these results.

Chronic alcohol feeding and its withdrawal on the structure and function of the rat liver plasma membrane: a study with 125I-labelled glucagon binding as a metabolic probe

1982 ◽  
Vol 60 (9) ◽  
pp. 1171-1176 ◽  
Author(s):  
Hung Lee ◽  
E. A. Hosein
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Structure And Function ◽  
Scatchard Analysis ◽  
Chronic Alcohol ◽  
Alcohol Administration ◽  
Liver Plasma Membranes ◽  
And Function ◽  
Chronic Alcohol Administration

The effect of chronic alcohol administration on the structure and function of the rat liver plasma membranes has been investigated. Chronic alcohol administration did not affect the yield of these membranes using conventional isolation procedures. The extent of plasma membrane enrichment or contamination with other interior membranes was identical in the control and alcoholic preparations. The binding of 125I-labelled glucagon to these experimental liver plasma membranes was significantly decreased. Scatchard analysis of the high affinity sites showed a significant reduction [Formula: see text] in receptor number rather than binding affinity, which was not altered. This anomaly persisted through 72-h withdrawal of alcohol. These data suggest that very stable changes were induced in these liver plasma membranes after prolonged alcohol ingestion.

scholarly journals Evidence for the extracellular reduction of ferricyanide by rat liver. A trans-plasma membrane redox system

1981 ◽  
Vol 200 (3) ◽  
pp. 565-572 ◽  
Author(s):  
Michael G. Clark ◽  
Eric J. Partick ◽  
Glen S. Patten ◽  
Frederick L. Crane ◽  
Hans Löw ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Redox System ◽  
Isolated Hepatocytes ◽  
Perfused Liver ◽  
Isolated Rat Hepatocytes ◽  
Plasma Membrane Redox System ◽  
Plasma Membrane Redox ◽  
High Affinity

1. Reduction of ferricyanide by the isolated perfused rat liver and by isolated rat hepatocytes was studied. 2. Ferricyanide was reduced to ferrocyanide by the perfused liver at a linear rate of 0.22μmol/min per g of liver. Ferricyanide was not taken up by the liver and the perfusate concentration of ferricyanide+ferrocyanide remained constant throughout the perfusion. Perfusate samples from livers perfused without ferricyanide did not reduce ferricyanide. 3. Isolated hepatocytes reduced ferricyanide in a biphasic manner. The initial rate of 2.3μmol/min per g of cells proceeded for approx. 3min and derived from low-affinity sites (apparent Km>1.3mm). The secondary rate of 0.29μmol/min per g of cells was maintained for the remainder of the incubation and derived from higher affinity sites (apparent Km0.13mm). Disruption of the cells resulted in an increase in the low-affinity rate and a decrease in the high-affinity rate. 4. Ferrocyanide was oxidized by isolated hepatocytes but not by perfused liver. The apparent Km for ferrocyanide oxidation by hepatocytes was 1.3mm. 5. Oxidized cytochrome c was reduced by isolated hepatocytes in the presence of 1mm-KCN but at a rate less than that of the reduction of ferricyanide. 6. Properties of the ferricyanide-reducing activities of intact hepatocytes and the perfused liver were examined. The low-affinity rate, present only in cell and broken cell preparations, was inhibited by 1μm-rotenone and 0.5mm-ferrocyanide, and stimulated by 0.1mm-KCN. The mitochondrial substrate, succinate, also stimulated this rate. The perfused liver showed only a high-affinity activity for ferricyanide reduction. This activity was also present in liver cells and was unaffected by rotenone, antimycin A, KCN, NaN3, or p-hydroxymercuribenzoate but was inhibited by 2.6mm-CaCl2, 2-heptyl-4-hydroxyquinoline-N-oxide and ferrocyanide. Overall, these results are consistent with the occurrence of a trans-plasma membrane redox system of liver that reduces extracellular ferricyanide to ferrocyanide. The reduction process shows properties which are similar to that of the NADH:ferricyanide oxidoreductase found in isolated liver plasma membranes but different from that of mitochondria.

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