scholarly journals Alterations in the activities of hepatic plasma-membrane and microsomal enzymes during liver regeneration

1983 ◽  
Vol 212 (2) ◽  
pp. 445-452 ◽  
Author(s):  
G Deliconstantinos ◽  
G Ramantanis
Keyword(s):  
Plasma Membrane ◽  
Liver Regeneration ◽  
Membrane Fluidity ◽  
Plasma Membranes ◽  
Membrane Lipids ◽  
Biological Significance ◽  
Hill Coefficient ◽  
Membrane Bound ◽  
The Hill ◽  
Membrane Bound Enzymes

A marked increase in the activities of rat liver plasma-membrane (Na+ + K+)-stimulated ATPase and microsomal Ca2+-stimulated ATPase was observed 18h after partial hepatectomy. Lipid analyses for both membrane preparations reveal that in partially hepatectomized rats the cholesterol and sphingomyelin content are decreased with a subsequent decrease in the cholesterol/phospholipid molar ratio compared with those of sham-operated animals. Changes in the allosteric properties of plasma-membrane (Na+ + K+)-stimulated ATPase by F- (as reflected by changes in the Hill coefficient) indicated a fluidization of the lipid bilayer of both membrane preparations in 18 h-regenerating liver. The amphipathic dodecyl glucoside incorporated into the hepatic plasma membranes evoked a marked increase in the (Na+ + K+)-stimulated ATPase and 5′-nucleotidase activities. The lack of effect of the glucoside on the Lubrol-PX-solubilized 5′-nucleotidase indicates that changes in the activities of the membrane-bound enzymes caused by the glucoside are due to modulation of the membrane fluidity. Dodecyl glucoside appears to increase the membrane fluidity, evaluated through changes in the Hill coefficient for plasma-membrane (Na+ + K+)-stimulated ATPase. The biological significance of these data is discussed in terms of the differences and changes in the interaction of membrane-bound enzymes with membrane lipids during liver regeneration.

Effect of prostaglandins E2 and F2α on membrane calcium binding, Ca2+/Mg2+-ATPase activity and membrane fluidity in rat myometrial plasma membranes

1986 ◽  
Vol 110 (3) ◽  
pp. 395-404 ◽  
Author(s):  
G. Deliconstantinos ◽  
S. Fotiou
Keyword(s):  
Membrane Fluidity ◽  
Calcium Binding ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Gradient Centrifugation ◽  
Hill Coefficient ◽  
Uterine Contractions ◽  
Enzymatic Regulation ◽  
Discontinuous Sucrose Gradient ◽  
The Hill

ABSTRACT Myometrial plasma membrane (MPM) preparations from rats treated with oestradiol were obtained by discontinuous sucrose-gradient centrifugation. The preparations contained calcium-stimulated and magnesium-dependent ATPase (Ca2+/Mg2+-ATPase). A dramatic decrease in the activity of Ca2+/Mg2+-ATPase was observed when preparations were treated with 0·025–10μmol protaglandins E2 and F2α (PGE2 and PGF2α)/l. In contrast, there was a marked increase in MPM-bound 5′-nucleotidase activity at low concentrations (up to 2 μmol/l) of PGE2 and PGF2α; higher concentrations (up to 10 μmol/l), however, led to a progressive inhibition of enzyme activity. Association (specific and non-specific binding) of PGE2 and PGF2α with MPM at pH 7 was found to require Ca2+ (half-maximal concentration approximately 0·7 mmol/l). Changes in the allosteric properties of MPM-bound 5′-nucleotidase by concanavalin A (as reflected by changes in the Hill coefficient) indicated a fluidization of the membrane induced by PGE2 and PGF2α. The steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene-labelled MPM decreased in PGE2- and PGF2α-treated MPM from 1·24 ± 0·04 (s.d.) to 0·66 ± 0·01 and 0·74 ± 0·01 respectively, which is consistent with a general increase in membrane fluidity. It is suggested that PGE2 and PGF2α promote changes in the physical properties of MPM which may be relevant to the induction of uterine contractions by enzymatic regulation of intracellular calcium concentrations. J. Endocr. (1986) 110, 395–404

Endogenous hyperphosphorylation in plasma membrane from an ascites hepatocarcinoma cell line

1988 ◽  
Vol 66 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Jon G. Church ◽  
Shobha Ghosh ◽  
Basil D. Roufogalis ◽  
Antonio Villalobo
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Cell Line ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Membrane Lipids ◽  
Normal Adult ◽  
Plasma Membrane Proteins ◽  
Phosphoprotein Phosphatase ◽  
Membrane Bound

Plasma-membrane-bound kinases of AS-30D ascites from transplantable rat hepatocarcinoma were shown to extensively catalyze the phosphorylation of plasma membrane proteins and membrane lipids, using [γ-32P]ATP or [γ-32P]GTP as a phosphate donor. In contrast, plasma membranes from normal adult rat liver or fast-growing regenerating liver (24 h after partial hepatectomy) produce significantly less activity for protein phosphorylation and little phosphorylation of the lipids. However, neonatal (24 h old) rat liver plasma membrane preparations show levels of phosphorylation of proteins and lipids intermediate between those in the tumor cell line and normal adult plasma membrane preparations. Phosphatidic acid was identified as one of the 32P-labelled lipids in the tumor plasma membrane chloroform–methanol (2:1, v/v) extract. Phosphorylation of protein was not affected by cAMP or cGMP. However, calcium ion (in the presence or absence of calmodulin) significantly modifies the 32P labelling of a series of proteins in normal tissue but has little effect with the neoplastic preparations. Some plasma membrane proteins were capable of nucleotide binding, instead or in addition to being phosphorylated. Finally, the presence of membrane-bound phosphoprotein phosphatase(s) was also demonstrated in all the preparations examined by means of chase experiments with nonlabelled ATP or GTP, and (or) by the use of the phosphoprotein phosphatase inhibitor, orthovanadate.

scholarly journals Large-scale purification of presynaptic plasma membranes from Torpedo marmorata electric organ.

1985 ◽  
Vol 101 (5) ◽  
pp. 1757-1762 ◽  
Author(s):  
N Morel ◽  
J Marsal ◽  
R Manaranche ◽  
S Lazereg ◽  
J C Mazie ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Large Scale ◽  
Plasma Membranes ◽  
Electric Organ ◽  
Acetylcholinesterase Activity ◽  
Cholinergic Nerve Terminals ◽  
Membrane Bound ◽  
Torpedo Electric Organ ◽  
Presynaptic Plasma Membrane ◽  
Glycera Convoluta

The presynaptic plasma membrane (PSPM) of cholinergic nerve terminals was purified from Torpedo electric organ using a large-scale procedure. Up to 500 g of frozen electric organ were fractioned in a single run, leading to the isolation of greater than 100 mg of PSPM proteins. The purity of the fraction is similar to that of the synaptosomal plasma membrane obtained after subfractionation of Torpedo synaptosomes as judged by its membrane-bound acetylcholinesterase activity, the number of Glycera convoluta neurotoxin binding sites, and the binding of two monoclonal antibodies directed against PSPM. The specificity of these antibodies for the PSPM is demonstrated by immunofluorescence microscopy.

scholarly journals Effect of Nedocromil Sodium on Polymorphonuclear Leukocyte Plasma Membrane

1994 ◽  
Vol 3 (7) ◽  
pp. S21-S24 ◽  
Author(s):  
A. Kantar ◽  
N. Oggiano ◽  
P. L. Giorgi ◽  
G. V. Coppa ◽  
R. Gabbianelli ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Steady State ◽  
Membrane Fluidity ◽  
Fluorescence Anisotropy ◽  
Polymorphonuclear Leukocyte ◽  
Polymorphonuclear Leukocytes ◽  
Plasma Membranes ◽  
Nedocromil Sodium ◽  
Plasma Membrane Fluidity ◽  
Steady State Fluorescence

The effect of nedocromil sodium on the plasma membrane fluidity of polymorphonuclear leukocytes (PMNs) was investigated by measuring steady-state fluorescence anisotropy of 1-[4-trimethylammonium-phenyl]-6-phenyl- 1,3,5-hexatriene (TMA-DPH) incorporated in the membrane. Our results show that nedocromil sodium 300 μM significantly decreased membrane fluidity of PMNs. The decrease in membrane fluidity of PMNs induced by fMLP was abolished in the presence of nedocromil sodium. These data suggest that nedocromil sodium interferes with the plasma membranes of PMNs and modulates their activities.

scholarly journals 5′-Nucleotidases of chicken gizzard and human pancreatic adenocarcinoma cells are anchored to the plasma membrane via a phosphatidylinositol–glycan

1989 ◽  
Vol 262 (1) ◽  
pp. 33-40 ◽  
Author(s):  
U Stochaj ◽  
K Flocke ◽  
W Mathes ◽  
H G Mannherz
Keyword(s):  
Plasma Membrane ◽  
Pancreatic Adenocarcinoma ◽  
Plasma Membranes ◽  
Chicken Gizzard ◽  
Human Pancreatic Adenocarcinoma ◽  
Adenocarcinoma Cells ◽  
Increased Sensitivity ◽  
Membrane Bound ◽  
Membrane Anchoring ◽  
Pancreatic Adenocarcinoma Cell Line

We have analysed the membrane anchorage of plasma-membrane 5′-nucleotidase, an ectoenzyme which can mediate binding to components of the extracellular matrix. We demonstrated that the purified enzyme obtained from chicken gizzard and a human pancreatic adenocarcinoma cell line were both completely transformed into a hydrophilic form by treatment with phospholipases C and D, cleaving glycosylphosphatidylinositol (GPI). These data indicate the presence of a glycolipid linker employed for membrane anchoring of the 5′-nucleotidase obtained from both sources. Incubation of plasma membranes under identical conditions revealed that about half of the AMPase activity was resistant to GPI-hydrolysing phospholipases. Investigation of the enzymic properties of purified chicken gizzard 5′-nucleotidase revealed only minor changes after removal of the phosphatidylinositol linker. However, cleavage of the membrane anchor resulted in an increased sensitivity towards inhibition by concanavalin A. After tissue fractionation, chicken gizzard 5′-nucleotidase could be obtained as either a membrane-bound or a soluble protein; the latter is suspected to be released from the plasma membrane by endogenous phospholipases. Higher-molecular-mass proteins immuno-cross-reactive with the purified chicken gizzard 5′-nucleotidase were detected as both soluble and membrane-bound forms.

scholarly journals ULTRASTRUCTURAL STUDY OF MEMBRANE-BOUND ENZYMES IN THYMOCYTES

1974 ◽  
Vol 22 (12) ◽  
pp. 1128-1134 ◽  
Author(s):  
ARIANE MONNERON ◽  
JEAN-CLAUDE BENICHOU ◽  
INSTITUT PASTEUR ◽  
YVETTE FLORENTIN ◽  
ELIANE GUERRY
Keyword(s):  
Plasma Membrane ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Uridine Diphosphate ◽  
Lead Phosphate ◽  
Isolated Nuclei ◽  
Whole Cells ◽  
Diphosphate Glucose ◽  
Membrane Bound ◽  
Membrane Bound Enzymes ◽  
Phosphate Deposits

Calf thymocytes in suspension, as well as isolated calf thymocyte nuclei, were incubated in the presence of several phosphorylated substrates. 5'-Nucleotidase was easily detected on the plasma membrane of thymocytes (external side), but could be demonstrated on isolated nuclei only to a small extent. No other substrates were detectably hydrolyzed by isolated nuclei except adenosine triphosphate and 3'-thymidine monophosphate. The surface of whole cells was found to be much more reactive. A 3'-nucleotidase activity was shown to occur on the plasma membrane of a number of thymocytes and produced large lead phosphate deposits, some of them protruding into the cytoplasm. Enzymic activities splitting β-nicotinamide adenine dinucleotide phosphate and uridine diphosphate glucose were also readily detectable on the surface of cells. Since the pattern of the lead phosphate deposits and the number of reactive cells varied with the added substrate, and since cells were compared with their isolated nuclei, the positive reactions were considered to indicate the presence (on the exposed membranes) of the corresponding enzymes on the exposed membranes.

Sign in / Sign up

Export Citation Format

Share Document