Dose-dependent influence of buprenorphine on the phospholipid composition of cat hepatocyte plasma membranes in hemorrhagic shock

1994 ◽  
Vol 118 (2) ◽  
pp. 856-858 ◽  
Author(s):  
G. F. Leskova ◽  
V. I. Udovichenko
Keyword(s):  
Hemorrhagic Shock ◽  
Plasma Membranes ◽  
Phospholipid Composition ◽  
Dose Dependent

scholarly journals Regulation of the thyroid NADPH-dependent H2O2 generator by Ca2+: studies with phenylarsine oxide in thyroid plasma membrane

1997 ◽  
Vol 321 (2) ◽  
pp. 383-388 ◽  
Author(s):  
Yves GORIN ◽  
Anne Marie LESENEY ◽  
Renée OHAYON ◽  
Corinne DUPUY ◽  
Jacques POMMIER ◽  
...  
Keyword(s):  
Nadph Oxidase ◽  
Plasma Membranes ◽  
Direct Action ◽  
Native Enzyme ◽  
Thiol Groups ◽  
Phenylarsine Oxide ◽  
Oxidoreductase Activity ◽  
H2o2 Formation ◽  
Partial Inactivation ◽  
Dose Dependent

Pig thyroid plasma membranes contain a Ca2+-dependent NADPH:O2 oxidoreductase, the thyroid NADPH-dependent H2O2 generator. This provided the H2O2 for the peroxidase-catalysed synthesis of thyroid hormones. The effect of the tervalent arsenical, phenylarsine oxide (PAO), on the NADPH oxidase was studied. PAO caused two directly related dose-dependent effects with similar half-effect concentrations of PAO (3 nmol of PAO/mg of protein): (i) partial inactivation of H2O2 formation by the Ca2+-stimulated enzyme, and (ii) desensitization of the enzyme activity to Ca2+. PAO had no effect on membranes that had been Ca2+-desensitized by α-chymotrypsin treatment. The NADPH oxidase in membranes treated with excess PAO had the same Vmax with and without Ca2+. This value was half the Vmax of the native enzyme. However, the Km for NADPH determined with Ca2+ (18 ƁM, identical with that of the native enzyme) was approx. one-third of the Km measured without Ca2+, showing the direct action of Ca2+ on the PAOŐenzyme complex. PAO had the same effects, partial inactivation and Ca2+ desensitization, on the NADPH:ferricyanide oxidoreductase activity of the NADPH oxidase, suggesting that PAO acts on the flavodehydrogenase entity of the enzyme. Both partial inactivation and Ca2+ desensitization were completely and specifically reversed by 2,3-dimercaptopropanol, partly reversed by dithiothreitol and not reversed by 2-mercaptoethanol, indicating that PAO binds to vicinal thiol groups. These results suggest that thiol groups are involved in the control of thyroid NADPH oxidase by Ca2+; PAO bound to vicinal thiols might alter the structure of the enzyme so that electron transfer occurs without Ca2+ but more slowly.

scholarly journals Chlorotetracycline as a fluorescent Ca2+ probe in pancreatic islet cells.

1978 ◽  
Vol 76 (3) ◽  
pp. 652-674 ◽  
Author(s):  
I B Täljedal
Keyword(s):  
Plasma Membranes ◽  
Islet Cells ◽  
Dependent Manner ◽  
Cell Surfaces ◽  
Noticeable Effect ◽  
Cell Plasma ◽  
Glass Capillaries ◽  
Asymmetrically Distributed ◽  
Dose Dependent ◽  
Dispersed Cells

Pancreatic islets, or suspensions of islet cells, from noninbred ob/ob-mice were incubated with chlorotetracycline and analyzed for Ca2+-dependent fluorescence in a microscope. Unless logarithmically transformed, signals from islets were asymmetrically distributed with unstable variance. Signals from cells pelleted in glass capillaries were more homogeneous and depended linearly on the thickness of the sample. The effect of sample thickness and a significant enhancement of fluorescence by alloxan suggest that beta-cells were involved in producing the signal from whole islets. The signal from dispersed cells was probably diagnostic of Ca2+ in beta-cell plasma membranes because it was suppressed by La3+ and had a spectrum indicative of an apolar micromilieu; fluorescent staining of cell surfaces was directly seen at high magnification. Fluorescence from cells was enhanced by 0.5-10 mM Ca2+ in a dose-dependent manner, whereas less than 0.5 mM Ca2+ saturated the probe alone in methanol. The signal from islets or dispersed cells was suppressed by 5 mM theophylline; that from cells was also suppressed by 0.5 mM 3-isobutyl-1-methylxanthine, 1.2 or 15 mM Mg2+, 3-20 mM D-glucose, and, to a lesser extent, 20 mM 3-O-methyl-D-glucose. D-glucose was more inhibitory in the absence than in the presence of Mg2+, as if Mg2+ and D-glucose influenced the same Ca2+ pool. L-glucose, D-mannopheptulose, or diazoxide had no noticeable effect and 20 mM bicarbonate was stimulatory. The results suggest that microscopy of chlorotetracycline-stained cells can aid in characterizing calcium pools of importance for secretion. Initiation of insulin release may be associated with an increas

Intracoronary naloxone in hemorrhagic shock: dose-dependent stereospecific effects

1985 ◽  
Vol 249 (2) ◽  
pp. H272-H277 ◽  
Author(s):  
R. B. Lechner ◽  
N. J. Gurll ◽  
D. G. Reynolds
Keyword(s):  
Cardiac Output ◽  
Arterial Pressure ◽  
Hemorrhagic Shock ◽  
Coronary Circulation ◽  
Opiate Receptors ◽  
Shock Treatment ◽  
Hemodynamic Effects ◽  
Pentobarbital Sodium ◽  
Shock Models ◽  
Dose Dependent

Treatment with naloxone improves cardiovascular function and survival in a variety of shock models, and numerous sites and mechanisms for its action have been proposed. Data presented in this article support the hypothesis that in hemorrhagic shock naloxone exerts its beneficial hemodynamic effects by acting primarily at cardiac opiate receptors. Naloxone or its stereoisomer (d-naloxone) were administered intravenously (iv) and directly into the coronary circulation (ic) in dogs anesthetized with pentobarbital sodium and subjected to hemorrhagic shock. Treatment with naloxone (2.0 mg/kg iv or 0.2 mg/kg ic) resulted in significant improvements in arterial pressure, myocardial contractility, and cardiac output. Treatment with saline or naloxone (0.2 mg/kg iv) were without beneficial effect. The hemodynamic responses to naloxone administered into the coronary circulation were dose dependent and stereospecific. These data support the hypothesis that naloxone exerts its salubrious effects in canine hemorrhagic shock by acting at cardiac opiate receptors.

Extracellular ATP induces a nonspecific permeability of thymocyte plasma membranes

1989 ◽  
Vol 67 (9) ◽  
pp. 495-502 ◽  
Author(s):  
Chakib El-Moatassim ◽  
Nicole Bernad ◽  
Jean-Claude Mani ◽  
Jacques Dornand
Keyword(s):  
Purinergic Receptors ◽  
Plasma Membranes ◽  
Divalent Cations ◽  
Extracellular Atp ◽  
Active Species ◽  
Extracellular Nucleotides ◽  
Dependent Manner ◽  
Specific Receptors ◽  
Atp Analogs ◽  
Dose Dependent

We have previously demonstrated that extracellular ATP can give medullary thymocytes the calcium message required for the induction of their blastogenesis, without mobilization of intracellular calcium. We describe here the effects of extracellular nucleotides on membrane permeability to monovalent and divalent cations in mouse thymocytes. Among all nucleotides tested, under physiological conditions, only ATP and, to a lesser extent, 2-methylthio-ATP, adenosine 5′-O-(3-thio-triphosphate), and ADP were able to depolarize thymocyte plasma membranes and to induce Na+ and Ca2+ influxes into thymocytes; other nonhydrolysable ATP analogs were only effective in the absence of Mg2+. The ATP-induced effects were inhibited in a dose-dependent manner by Mg2+ and greatly potentiated in its absence, which suggests that the tetrabasic ATP4− is probably the active species and that a phosphotransferase activity is not involved in its effects. These ATP-mediated changes in ion fluxes result from an increase in nonspecific permeability of thymocyte membranes, probably by pore formation. These ion flux changes might be responsible for the mitogenic induction of phorbol 12-myristate 13-acetate treated medullary thymocytes. The potency order for the adenine derivatives to affect these fluxes (ATP>ADP> >AMP>adenosine) suggests the presence of ATP specific receptors (P2 purinergic receptors) on thymocyte plasma membranes.Key words: purinergic receptors, extracellular ATP, membrane potential, cation fluxes, thymocytes.

scholarly journals Cross-talk between glucagon- and adenosine-mediated signalling systems in rat hepatocytes: effects on cyclic AMP-phosphodiesterase activity

1995 ◽  
Vol 312 (3) ◽  
pp. 763-767 ◽  
Author(s):  
M Robles-Flores ◽  
G Allende ◽  
E Piña ◽  
J A García-Sáinz
Keyword(s):  
Cyclic Amp ◽  
Pertussis Toxin ◽  
Plasma Membranes ◽  
Rat Hepatocytes ◽  
Dependent Manner ◽  
Phosphodiesterase Activity ◽  
Cyclic Amp Phosphodiesterase ◽  
Cyclic Amp Accumulation ◽  
A1 Adenosine Receptors ◽  
Dose Dependent

The effect of adenosine analogues on glucagon-stimulated cyclic AMP accumulation in rat hepatocytes was explored. N6-Cyclopentyladenosine (CPA), 5′-N-ethylcarboxamidoadenosine and N6-(R-phenylisopropyl)adenosine inhibited in a dose-dependent manner the cyclic AMP accumulation induced by glucagon. This effect seems to be mediated through A1 adenosine receptors. Pertussis toxin completely abolished the effect of CPA on glucagon-stimulated cyclic AMP accumulation in whole cells which suggested that a pertussis-toxin-sensitive G-protein was involved. On the other hand, this action of adenosine analogues on glucagon-induced cyclic AMP accumulation was reverted by the selective low-Km cyclic AMP-phosphodiesterase inhibitor Ro 20-1724. Analysis of cyclic AMP-phosphodiesterase activity in purified hepatocyte plasma membranes showed that glucagon in the presence of GTP inhibited basal PDE activity by 45% and that CPA reverted this inhibition in dose-dependent manner. In membranes derived from pertussis-toxin-treated rats, we observed no inhibition of cyclic AMP-phosphodiesterase activity by glucagon in the absence or presence of CPA. Our results indicate that in hepatocyte plasma membranes, stimulation of adenylate cyclase activity and inhibition of a low-Km cyclic AMP phosphodiesterase activity are co-ordinately regulated by glucagon, and that A1 adenosine receptors can inhibit glucagon-stimulated cyclic AMP accumulation by blocking glucagon's effect on phosphodiesterase activity.

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