scholarly journals Simultaneous Measurements of Cytoplasmic K+ Concentration and the Plasma Membrane Electrical Parameters in Single Membrane Samples of Chara corallina

1986 ◽  
Vol 82 (2) ◽  
pp. 417-422 ◽  
Author(s):  
Mary J. Beilby ◽  
Michael R. Blatt
Keyword(s):  
Plasma Membrane ◽  
Chara Corallina ◽  
Electrical Parameters ◽  
Simultaneous Measurements ◽  
Single Membrane ◽  
K Concentration

A novel H+ permeability dominating intracellular pH in the early mouse embryo

Development ◽  
1993 ◽  
Vol 118 (4) ◽  
pp. 1353-1361
Author(s):  
J.M. Baltz ◽  
J.D. Biggers ◽  
C. Lechene
Keyword(s):  
Plasma Membrane ◽  
Intracellular Ph ◽  
Inner Cell Mass ◽  
Cell Mass ◽  
Cell Types ◽  
Preimplantation Embryos ◽  
Developmentally Regulated ◽  
Cell Stage ◽  
K Concentration ◽  
Early Mouse

Most cell types are relatively impermeant to H+ and are able to regulate their intracellular pH by means of plasma membrane proteins, which transport H+ or bicarbonate across the membrane in response to perturbations of intracellular pH. Mouse preimplantation embryos at the 2-cell stage, however, do not appear to possess specific pH-regulatory mechanisms for relieving acidosis. They are, instead, highly permeable to H+, so that the intracellular pH in the acid and neutral range is determined by the electrochemical equilibrium of H+ across the plasma membrane. When intracellular pH is perturbed, the rate of the ensuing H+ flux across the plasma membrane is determined by the H+ electrochemical gradient: its dependence on external K+ concentration indicates probable dependence on membrane potential and the rate depends on the H+ concentration gradient across the membrane. The large permeability at the 2-cell stage is absent or greatly diminished in the trophectoderm of blastocysts, but still present in the inner cell mass. Thus, the permeability to H+ appears to be developmentally regulated.

scholarly journals Kinetic study of the plasma-membrane potential in procyclic and bloodstream forms of Trypanosoma brucei brucei using the fluorescent probe bisoxonol

1996 ◽  
Vol 314 (2) ◽  
pp. 595-601 ◽  
Author(s):  
Fabienne DEFRISE-QUERTAIN ◽  
Chantal FRASER-L'HOSTIS ◽  
Danièle CORAL ◽  
Jacques DESHUSSES
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Trypanosoma Brucei ◽  
Cultured Cells ◽  
Bloodstream Form ◽  
Metabolic Inhibitors ◽  
Trypanosoma Brucei Brucei ◽  
Plasma Membrane Potential ◽  
Regulation Mechanisms ◽  
K Concentration

The characteristics of the plasma-membrane potential of procyclic and bloodstream forms of Trypanosoma brucei brucei (cultured cells) were investigated using the fluorescent anionic probe bisoxonol. Observation of a stable and representative plasma-membrane potential in the resting state required careful washing, centrifugation and maintenance of the cells at room temperature before measurement. Bloodstream forms were more prone to depolarization during washing at 4 °C than procyclic cells. The higher fluorescence observed in the presence of long slender cells than in the presence of procyclic cells shows that the plasma-membrane potential is more negative in the insect form. Healthy dilute cells can sustain their plasma-membrane potential for hours in the presence of external glucose. The presence of a high K+ concentration in the medium did not promote by itself the depolarization of either type of cell. Study of bisoxonol fluorescence as a function of time allowed us to follow the kinetics of the action of metabolic inhibitors in the presence of various ions. o-Vanadate (1 mM) was found to depolarize bloodstream-form cells rapidly but only in a phosphate-free NaCl buffer. Omeprazole and strophanthidin also specifically depolarized bloodstream-form trypanosomes. However, NN´-dicyclohexylcarbodi-imide depolarized both types of cell, but more rapidly for bloodstream-form cells. Bloodstream-form trypanosomes appear to use mainly a vanadate-sensitive Na+ pump to maintain their Na+-diffusion gradient. However, most of the ATPase inhibitors tested had little or no effect on the plasma-membrane potential of procyclics suggesting that this form of trypanosome may rely on several regulation mechanisms.

scholarly journals Control of phosphate transport across the plasma membrane of Chara corallina

1998 ◽  
Vol 49 (318) ◽  
pp. 13-19 ◽  
Author(s):  
T. Mimura ◽  
R. J. Reid ◽  
F. A. Smith
Keyword(s):  
Plasma Membrane ◽  
Phosphate Transport ◽  
Chara Corallina

Na+-K+-ATPase inhibition stimulates PGE release in guinea pig taenia coli

1977 ◽  
Vol 232 (5) ◽  
pp. C191-C195 ◽  
Author(s):  
R. F. Coburn ◽  
S. Soltoff
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Guinea Pig ◽  
Prostaglandin E ◽  
Taenia Coli ◽  
Na Pump ◽  
Membrane Enzyme ◽  
K Concentration ◽  
Atpase Inhibition ◽  
Prostaglandin E Release

Inhibition of the plasma membrane enzyme Na+-K+-ATPase by ouabain zero extracellular K+, or low extracellular Na+, markedly augmented prostaglandin E release from the guinea pig taenia coli. Data suggest this phenomenon may be linked directly to Na+-K+-ATPase or Na+ pump activities, or changes in intracellular K+ concentration. The augmented prostaglandin E release was not due to changes in intracellular Na+, Ca2+, pH, or membrane potential, resulting from Na+ pump inhibition. The characteristics of the plasma membrane may exert a control on prostaglandin E release in this smooth muscle.

Effect of inhibitors of gastric secretion on polarization of gastric potential by voltage clamping

1993 ◽  
Vol 264 (4) ◽  
pp. G630-G636
Author(s):  
G. Carrasquer ◽  
J. Y. Zhang ◽  
X. Wu ◽  
W. S. Rehm ◽  
M. Schwartz
Keyword(s):  
Plasma Membrane ◽  
Gastric Mucosa ◽  
Gastric Secretion ◽  
Proton Pump ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
Luminal Membrane ◽  
Voltage Clamping ◽  
K Concentration ◽  
Effect Of Inhibitors

Voltage clamping across the frog gastric mucosa, nutrient positive to secretory, results in an increase in the open-circuit potential difference (OCPD). The increase in OCPD, or polarization, induced by voltage clamping could be caused by a redistribution of ions across the plasma membrane or by a polarization of pump electromotive forces, such as the Na(+)-K(+)-adenosinetriphosphatase (ATPase) located in the nutrient (serosal) membrane or the proton pump located in the secretory (luminal) membrane. The polarization induced by voltage clamping was not affected by removing Cl- and Na+ or by increasing the K+ concentration to 79 mM but was markedly reduced by placing in the nutrient solution 10(-3) M famotidine or 10(-4) M omeprazole. These data suggest that there is a strong contribution of the proton pump to the polarization induced by voltage clamping with some contribution of ion redistribution and/or the Na(+)-K(+)-ATPase. The data support the electrogenicity of the proton pump.

scholarly journals Changes in cytosolic Mg2+ levels can regulate the activity of the plasma membrane H+-ATPase in maize

2011 ◽  
Vol 435 (1) ◽  
pp. 93-101 ◽  
Author(s):  
Stefan Hanstein ◽  
Xiaozhi Wang ◽  
Xiaoqing Qian ◽  
Peter Friedhoff ◽  
Ammara Fatima ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Stress Responses ◽  
Kinetic Modelling ◽  
Membrane Vesicles ◽  
Hydrolytic Activity ◽  
Competitive Inhibitor ◽  
Order Of Magnitude ◽  
Atp Inhibition ◽  
K Concentration ◽  
Low K

Plant PM (plasma membrane) H+-ATPase, a major consumer of cellular ATP, is driven by the MgATP complex which may dissociate at low cytosolic Mg2+ activity. We investigated whether hydrolytic activity of PM H+-ATPase is inhibited at ATP concentrations exceeding the Mg2+ concentration. Activity in isolated maize PMs was measured at pH 6.5 in the presence of 5 mM Mg2+ (high) or 2 mM Mg2+ (low), whereas K+ was applied at concentrations of 155 mM (high) or 55 mM (low). In all experiments, with membrane vesicles either from roots or leaves, the enzyme activity decreased in the presence of Mg2+-free ATP. At inhibitory ATP concentrations, the activity was not influenced by the K+ concentration. The activity was restored after increasing the Mg2+ concentration. ATP inhibition also occurred at pH 7.5. Kinetic modelling shows that Mg2+-free ATP acted as a competitive inhibitor with a Ki in the range of the Km. Ki decreased by 75% at low K+ concentration. Ki was one order of magnitude lower at pH 7.5 compared with pH 6.5. The observed inhibition is consistent with a concept in which down-regulation of the cytosolic Mg2+ activity is involved in (phyto)hormonal stress responses.

scholarly journals Ca2+-dependent and Ca2+-independent degradation of phosphatidylinositol in rabbit vas deferens

1981 ◽  
Vol 194 (1) ◽  
pp. 129-136 ◽  
Author(s):  
K Egawa ◽  
B Sacktor ◽  
T Takenawa
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Vas Deferens ◽  
The Other ◽  
Ionophore A23187 ◽  
K Concentration ◽  
Rabbit Vas Deferens ◽  
Dependent Mechanism ◽  
Stimulation Of

The effects of Ca2+ and acetylcholine on the degradation and synthesis of phosphatidylinositol in rabbit vas deferens was studied in vitro by a pulse–chase technique and by measuring the content of the phospholipid in the tissue. Ca2+-dependent degradation of phosphatidylinositol was found in slices and homogenates prelabelled with myo-[2-3H]inositol. The phosphatidylinositol content of the slices also decreased by a Ca2+-dependent mechanism. On the other hand, removal of intracellular Ca2+ with the ionophore A23187 and EGTA increased the amount of phosphatidylinositol. These results indicate that the intracellular Ca2+ concentration has an important role in regulating the phosphatidylinositol content of the tissue. Increasing the extracellular K+ concentration, which causes an increase in plasma-membrane Ca2+ permeability, did not enhance phosphatidylinositol breakdown nor decrease its tissue content. However, phosphatidylinositol synthesis was clearly inhibited. After stimulation of the smooth muscle with acetylcholine, degradation of phosphatidylinositol was enhanced. Furthermore, the content of phosphatidylinositol in the tissue also decreased. These phenomena were evident even in the absence of Ca2+. The acetylcholine-induced degradation of phosphatidylinositol was blocked by the muscarinic antagonist atropine, but not by the nicotinic antagonist (+)-tubocurarine. The acetylcholine-induced decrease in the phosphatidylinositol content of the tissue led to the compensatory synthesis of phosphatidylinositol. Synthesis was separated from degradation in the same tissue. Compensatory synthesis was inhibited by acetylcholine. The degradation of phosphatidylinositol induced by acetylcholine was not inhibited by 8-bromoguanosine 3′:5′-cyclic monophosphate, indicating that the degradative process was not mediated by an increase in the cyclic nucleotide.

Sign in / Sign up

Export Citation Format

Share Document