scholarly journals Electrolyte Metabolism in HeLa Cells

1963 ◽  
Vol 46 (6) ◽  
pp. 1303-1315 ◽  
Author(s):  
Margaret Wickson-ginzburg ◽  
A. K. Solomon
Keyword(s):  
Transport System ◽  
Hela Cells ◽  
Generation Time ◽  
Chemical Concentration ◽  
Concentration Gradients ◽  
K Uptake ◽  
Initial Value ◽  
Electrolyte Metabolism ◽  
K Cells ◽  
Low K

Methods have been developed to study cellular Na, K, and Cl concentrations in HeLa cells. Cell [Na] and [K] are functions of the age of the culture. As the culture grows [K], expressed in mmols/liter cell H2O, rises from an initial value of 121 to a peak of 206 at about 4 days, and thereafter falls until it has almost returned to the initial value by the 9th day. [Na] falls as [K] rises, but there is no fixed relationship between the cellular concentrations of the two cations. There is, however, a correlation between generation time and cellular [K]. Measurements of net K uptake and net Na extrusion were carried out during 1 hour incubation at 37°C of low K cells. Both net K uptake and net Na extrusion took place against chemical concentration gradients, so that at least one transport system must be active; if the Cl distribution is passive both net K uptake and net Na extrusion are active. Studies with inhibitors of respiration and glycolysis lead to the conclusion that respiration is not required for these net transports, which appear to derive their energy from glycolytic sources.

scholarly journals Net Uptake of Potassium in Neurospora Exchange for sodium and hydrogen ions

1968 ◽  
Vol 52 (3) ◽  
pp. 424-443 ◽  
Author(s):  
Clifford L. Slayman ◽  
Carolyn W. Slayman
Keyword(s):  
Transport System ◽  
Potassium Uptake ◽  
Hydrogen Ions ◽  
Cell Water ◽  
K Uptake ◽  
Respiratory Inhibition ◽  
Net Uptake ◽  
Order Of Magnitude ◽  
External Site ◽  
Low K

Net uptake of potassium by low K, high Na cells of Neurospora at pH 5.8 is accompanied by net extrusion of sodium and hydrogen ions. The amount of potassium taken up by the cells is matched by the sum of sodium and hydrogen ions lost, under a variety of conditions: prolonged preincubation, partial respiratory inhibition (DNP), and lowered [K]o. All three fluxes are exponential with time and obey Michaelis kinetics as functions of [K]o. The Vmax for net potassium uptake, 22.7 mmoles/kg cell water/min, is very close to that for K/K exchange reported previously (20 mmoles/kg cell water/min). However, the apparent Km for net potassium uptake, 11.8 mM [K]o, is an order of magnitude larger than the value (1 mM) for K/K exchange. It is suggested that a single transport system handles both net K uptake and K/K exchange, but that the affinity of the external site for potassium is influenced by the species of ion being extruded.

On the structural organization of biological pumps and channels

1984 ◽  
Vol 42 ◽  
pp. 138-141
Author(s):  
G. Zampighi ◽  
M. Kreman
Keyword(s):  
Active Transport ◽  
Transport System ◽  
Plasma Membranes ◽  
Transport Proteins ◽  
Molecular Organization ◽  
Passive Transport ◽  
Concentration Gradients ◽  
Cell Functions ◽  
Natural Concentration ◽  
Active Transport System

The plasma membranes of most animal cells contain transport proteins which function to provide passageways for the transported species across essentially impermeable lipid bilayers. The channel is a passive transport system which allows the movement of ions and low molecular weight molecules along their concentration gradients. The pump is an active transport system and can translocate cations against their natural concentration gradients. The actions and interplay of these two kinds of transport proteins control crucial cell functions such as active transport, excitability and cell communication. In this paper, we will describe and compare several features of the molecular organization of pumps and channels. As an example of an active transport system, we will discuss the structure of the sodium and potassium ion-activated triphosphatase [(Na+ +K+)-ATPase] and as an example of a passive transport system, the communicating channel of gap junctions and lens junctions.

scholarly journals Aspects of potassium and magnesium uptake by oats.

1974 ◽  
Vol 22 (4) ◽  
pp. 237-244
Author(s):  
A.C. Schuffelen
Keyword(s):  
Direct Relationship ◽  
Common Mechanism ◽  
Specific Mechanism ◽  
K Uptake ◽  
Uptake Mechanism ◽  
Water Culture ◽  
Mg Deficiency ◽  
Magnesium Uptake ◽  
Low K ◽  
Solution Acidity

Data from a range of experiments with oats in water culture indicated that the occurrence of Mg deficiency had only a slight direct relationship with solution acidity. It was calculated that about 3% of the total mechanism for the uptake of K and Mg consisted of a specific mechanism for Mg uptake, 30% of a specific mechanism for K uptake, and 67% of a common mechanism. It was not clear whether one or more systems were involved. At very low K concentrations the specific K uptake mechanism could also take up Na. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals ZMK1 Is Involved in K+ Uptake and Regulated by Protein Kinase ZmCIPK23 in Zea mays

2021 ◽  
Vol 12 ◽  
Author(s):  
Wu Han ◽  
Yun Ji ◽  
Wei Wu ◽  
Jin-Kui Cheng ◽  
Han-Qian Feng ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Growth And Development ◽  
Mineral Elements ◽  
Plant Roots ◽  
Plant Growth And Development ◽  
K Uptake ◽  
Uptake Mechanism ◽  
Uptake Activity ◽  
Electrophysiological Characterization ◽  
Low K

Potassium (K+) is one of essential mineral elements for plant growth and development. K+ channels, especially AKT1-like channels, play crucial roles in K+ uptake in plant roots. Maize is one of important crops; however, the K+ uptake mechanism in maize is little known. Here, we report the physiological functions of K+ channel ZMK1 in K+ uptake and homeostasis in maize. ZMK1 is a homolog of Arabidopsis AKT1 channel in maize, and mainly expressed in maize root. Yeast complementation experiments and electrophysiological characterization in Xenopus oocytes indicated that ZMK1 could mediate K+ uptake. ZMK1 rescued the low-K+-sensitive phenotype of akt1 mutant and enhanced K+ uptake in Arabidopsis. Overexpression of ZMK1 also significantly increased K+ uptake activity in maize, but led to an oversensitive phenotype. Similar to AKT1 regulation, the protein kinase ZmCIPK23 interacted with ZMK1 and phosphorylated the cytosolic region of ZMK1, activating ZMK1-mediated K+ uptake. ZmCIPK23 could also complement the low-K+-sensitive phenotype of Arabidopsis cipk23/lks1 mutant. These findings demonstrate that ZMK1 together with ZmCIPK23 plays important roles in K+ uptake and homeostasis in maize.

Energetics of sugar transport by isolated intestinal epithelial cells: effects of cytochalasin B

1979 ◽  
Vol 237 (1) ◽  
pp. C56-C63 ◽  
Author(s):  
G. A. Kimmich ◽  
J. Randles
Keyword(s):  
Steady State ◽  
Epithelial Cells ◽  
Transport System ◽  
Cytochalasin B ◽  
Intestinal Epithelial Cells ◽  
Sugar Accumulation ◽  
Facilitated Diffusion ◽  
Intestinal Epithelial ◽  
Passive System ◽  
Concentration Gradients

The capability of isolated intestinal epithelial cells to establish concentration gradients of 3-O-methylglucose (3-OMG) by a Na+-dependent transport system is limited by concomitant function of a Na+-independent, facilitated diffusion transport system. Monosaccharides accumulated by the active system are continuously lost via the passive system, which acts to lower steady-state sugar gradients maintained by the cell. Cytochalasin B is a potent inhibitor of the passive system and allows the cells to establish a sugar gradient that is much higher than normal. When extracellular [3-;OMG] is 1 mM, cytochalasin induces sugar accumulation ratios of 30-;fold (+/- phlorizin) in contrast to control ratios of approximately 10-;fold. When [3-;OMG] is 0.1 mM, cytochalasin (0.1 mM) induces 40-;fold accumulation ratios. When changes in extracellular sugar concentration are considered, steady-state concentration gradients observed are 70-;fold. For a Na:sugar coupling stoichiometry of 1:1, gradients of this magnitude represent the approximate theoretical maximum for a transport system driven exclusively by the transmembrane electrochemical potential for Na+.

Volume and anion dependency of ouabain-resistant K-Rb fluxes in sheep red blood cells

1988 ◽  
Vol 255 (3) ◽  
pp. C331-C339 ◽  
Author(s):  
P. K. Lauf
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Cell Types ◽  
Sheep Red Blood Cells ◽  
K Cells ◽  
High K ◽  
Before And After ◽  
Volume Response ◽  
Altered Cell ◽  
Low K

The effect of six different anions on the volume response of ouabain-resistant K transport was systematically studied at extracellular pH (pHo) = 7.4 in sheep red blood cells of both low and high K genotype before and after treatment with the sulfhydryl (SH) reagent N-ethylmaleimide (NEM). In methanesulfonate (CH3SO3), both the apparent Rb permeability (P(app)Rb), calculated from ouabain-resistant Rb influx), and K permeability (PK, calculated from the rate constants of ouabain-resistant zero-trans K efflux, 0k(OR)K) were volume independent and close to 10(-10) cm/s for both cell types, but in Cl, Br, I, SCN, and NO3 they were significantly different in low and high K cells with altered cell volumes. Thus, in 15% osmotically shrunken low K cells, P(app)Rb) and PK were similar regardless of the anions present, but upon 10-15% swelling, they increased to approximately 4-6 X 10(-9) cm/s in Br and 2 X 10(-9) cm/s in Cl and also increased with comparatively small increments in I, SCN, and NO3. Treatment with NEM enhanced both P(app)Rb) and PK, particularly in shrunken low K cells, to approximately 10(-8) cm/s in Br and Cl but not in I, SCN, and NO3. In shrunken or isotonic high K cells, P(app)Rb) and PK were close to 10(-10) cm/s in all anions except for SCN. Swelling and/or NEM increased PK and P(app)Rb) in Cl and Br only two- to threefold.(ABSTRACT TRUNCATED AT 250 WORDS)

A low K+signal is required for functional high-affinity K+uptake through HAK5 transporters

2014 ◽  
Vol 152 (3) ◽  
pp. 558-570 ◽  
Author(s):  
Francisco Rubio ◽  
Mario Fon ◽  
Reyes Ródenas ◽  
Manuel Nieves-Cordones ◽  
Fernando Alemán ◽  
...  
Keyword(s):  
K Uptake ◽  
High Affinity ◽  
Low K

scholarly journals Trk1 and Trk2 Define the Major K+Transport System in Fission Yeast

2000 ◽  
Vol 182 (2) ◽  
pp. 394-399 ◽  
Author(s):  
Fernando Calero ◽  
Néstor Gómez ◽  
Joaquín Ariño ◽  
José Ramos
Keyword(s):  
Fission Yeast ◽  
Transport System ◽  
Budding Yeast ◽  
Genome Database ◽  
Putative Gene ◽  
Transport Component ◽  
Increased Sensitivity ◽  
Potassium Influx ◽  
Low K ◽  
K Transport

ABSTRACT The trk1 + gene has been proposed as a component of the K+ influx system in the fission yeastSchizosaccharomyces pombe. Previous work from our laboratories revealed that trk1 mutants do not show significantly altered content or influx of K+, although they are more sensitive to Na+. Genome database searches revealed that S. pombe encodes a putative gene (designated here trk2 +) that shows significant identity totrk1 +. We have analyzed the characteristics of potassium influx in S. pombe by using trk1 trk2mutants. Unlike budding yeast, fission yeast displays a biphasic transport kinetics. trk2 mutants do not show altered K+ transport and exhibit only a slightly reduced Na+ tolerance. However, trk1 trk2 double mutants fail to grow at low K+ concentrations and show a dramatic decrease in Rb+ influx, as a result of loss of the high-affinity transport component. Furthermore, trk1 trk2cells are very sensitive to Na+, as would be expected for a strain showing defective potassium transport. When trk1 trk2 cells are maintained in K+-free medium, the potassium content remains higher than that of the wild type ortrk single mutants. In addition, the trk1 trk2strain displays increased sensitivity to hygromycin B. These results are consistent with a hyperpolarized state of the plasma membrane. An additional phenotype of cells lacking both Trk components is a failure to grow at acidic pH. In conclusion, the Trk1 and Trk2 proteins define the major K+ transport system in fission yeast, and in contrast to what is known for budding yeast, the presence of any of these two proteins is sufficient to allow growth at normal potassium levels.

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