scholarly journals Resolution of the potassium ion pump in muscle fibers using barium ions.

1975 ◽  
Vol 66 (3) ◽  
pp. 269-286 ◽  
Author(s):  
R A Sjodin ◽  
O Ortiz
Keyword(s):  
Membrane Permeability ◽  
Passive Movement ◽  
Ion Pump ◽  
Pumping Rate ◽  
Barium Ions ◽  
Rectangular Hyperbola ◽  
Wide Range ◽  
Na Ions ◽  
Frog Sartorius ◽  
External K

When frog sartorius muscles recover from Na enrichment in the presence of external K, net K entry into the fibers occurs by both passive movement and active inward transport via a K pump. Under normal conditions, it has not been possible to experimentally distinguish these processes. Fractionation into the flux components must be accomplished from inferences concerning the K conductance or permeability during a period of rapid Na extrusion. The best estimates indicate that 60-80% of the K entry occurs via the K pump. In the presence of Ba ions, the membrane permeability to K is very much reduced. Under these conditions, Na-enriched muscles underwent a normal recovery in the presence of external K, and the amount of inward K movement due to the K pump rose to over 90% of the total K entry. The characteristics of the K pump studied by this means were: (a) essentially complete inhibition by 10(-4) M ouabain, (b) inhibition by [Na]omicron, (c) activation by [K]omicron according to a rectangular hyperbola in the absence of [Na]omicron, (d) linear activation by [Na]iota over a wide range in concentration, (e) zero or undetectably low pumping rate as [Na]iota leads to 0, (f) the number of Na ions actively transported per K ion actively transported is 1.4-1.7 normally and 1.1 in the presence of Ba.

scholarly journals Changes in the Membrane Permeability of Frog's Sartorius Muscle Fibers in Ca-Free EDTA Solution

1963 ◽  
Vol 47 (2) ◽  
pp. 379-392 ◽  
Author(s):  
H. Kimizuka ◽  
K. Koketsu
Keyword(s):  
Membrane Permeability ◽  
Chloride Content ◽  
Chloride Ions ◽  
Sartorius Muscle ◽  
Constant Field ◽  
Sodium Influx ◽  
Sodium Potassium ◽  
Edta Solution ◽  
Frog Sartorius ◽  
Sodium And Potassium

The changes in the membrane permeability to sodium, potassium, and chloride ions as well as the changes in the intracellular concentration of these ions were studied on frog sartorius muscles in Ca-free EDTA solution. It was found that the rate constants for potassium and chloride efflux became almost constant within 10 minutes in the absence of external calcium ions, that for potassium increasing to 1.5 to 2 times normal and that for chloride decreasing about one-half. The sodium influx in Ca-free EDTA solution, between 30 and 40 minutes, was about 4 times that in Ringer's solution. The intracellular sodium and potassium contents did not change appreciably but the intracellular chloride content had increased to about 4 times normal after 40 minutes. By applying the constant field theory to these results, it was concluded that (a) PCl did not change appreciably whereas PK decreased to a level that, in the interval between 10 and 40 minutes, was about one-half normal, (b) PNa increased until between 30 and 40 minutes it was about 8 times normal. The low value of the membrane potential between 30 and 40 minutes was explained in terms of the changes in the membrane permeability and the intracellular ion concentrations. The mechanism for membrane depolarization in this solution was briefly discussed.

scholarly journals Effect of acetylcholine on postjunctional membrane permeability in eel electroplaque.

1977 ◽  
Vol 70 (1) ◽  
pp. 23-36 ◽  
Author(s):  
N L Lassignal ◽  
A R Martin
Keyword(s):  
Field Equation ◽  
Membrane Potential ◽  
Membrane Permeability ◽  
Ionic Composition ◽  
Reversal Potential ◽  
Resting Potential ◽  
Constant Field ◽  
Free Solution ◽  
Positive Direction ◽  
External K

Acetylcholine (ACh) was applied iontophoretically to the innervated face of isolated eel electroplaques while the membrane potential was being recorded intracellularly. At the resting potential (about -85 mV) application of the drug produced depolarizations (ACh potentials) of 20 mV or more which became smaller when the membrane was depolarized and reversed in polarity at about zero membrane potential. The reversal potential shifted in the negative direction when external Na+ was partially replaced by glucosamine. Increasing external K+ caused a shift of reversal potential in the positive direction. It was concluded that ACh increased the permeability of the postjunctional membrane to both ions. Replacement of Cl- by propionate had no effect on the reversal potential. In Na+-free solution containing glucosamine the reversal potential was positive to the resting potential, suggesting that ACh increased the permeability to glucosamine. Addition of Ca++ resulted in a still more positive reversal potential, indicating an increased permeability to Ca++ as well. Analysis of the results indicated that the increases in permeability of the postjunctional membrane to K+, Na+, Ca++, and glucosamine were in the ratios of approximately 1.0:0.9:0.7:0.2, respectively. With these permeability ratios, all of the observed shifts in reversal potential with changes in external ionic composition were predicted accurately by the constant field equation.

scholarly journals Tracer and Non-Tracer Potassium Fluxes in Frog Sartorius Muscle and the Kinetics of Net Potassium Movement

1964 ◽  
Vol 47 (4) ◽  
pp. 605-638 ◽  
Author(s):  
R. A. Sjodin ◽  
E. G. Henderson
Keyword(s):  
Specific Activity ◽  
Small Deviation ◽  
Sartorius Muscle ◽  
Potassium Efflux ◽  
Cellular Compartment ◽  
Ringer’S Solution ◽  
Frog Sartorius Muscle ◽  
Wide Range ◽  
Whole Muscle ◽  
Frog Sartorius

Experiments were performed to test the applicability of permeability kinetics to whole frog sartorius muscle using K42 ions as tracers of potassium flux. The whole muscle was found to obey closely the kinetic laws expected to hold for single cellular units in which the potassium fluxes are membrane-limited and intracellular mixing is rapid enough not to introduce serious error. In a 5 mM K Ringer's solution, potassium efflux was very nearly equal to influx when the rate constant for K42 loss was applied to the whole of the muscle potassium. Over a fairly wide range of external potassium concentration, the assumed unidirectional fluxes measured with tracer K42 showed good agreement with net potassium changes determined analytically. The specific activity of potassium lost from labeled muscles to an initially K-free Ringer's solution was measured as a test of the adequacy of intracellular mixing. The results were those expected for a population of cells with uniformly distributed intracellular K42. A small deviation was encountered which can be attributed either to a dispersion of fiber sizes in the sartorius or to a possible small additional cellular compartment in each individual fiber. The additional cellular compartment, should it exist, contains from 0.5 to 1 per cent of the muscle potassium. This is evidently not large enough to interfere seriously with the applicability of permeability kinetics to the whole muscle.

scholarly journals The Ionic Mechanisms of Hyperpolarizing Responses in Lobster Muscle Fibers

1961 ◽  
Vol 45 (2) ◽  
pp. 243-265 ◽  
Author(s):  
J. P. Reuben ◽  
R. Werman ◽  
H. Grundfest
Keyword(s):  
Membrane Permeability ◽  
Muscle Fibers ◽  
Membrane Resistance ◽  
Oscillatory Behavior ◽  
Current Leads ◽  
Oscillatory Characteristic ◽  
Ionic Mechanisms ◽  
External K

Lobster muscle fibers develop hyperpolarizing responses when subjected to sufficiently strong hyperpolarizing currents. In contrast to axons of frog, toad, and squid, the muscle fibers produce their responses without the need for prior depolarization in high external K+. Responses begin at a threshold polarization (50 to 70 mv), the potential reaching 150 to 200 mv hyperpolarization while the current remains constant. The increased polarization develops at first slowly, then becomes rapid. It usually subsides from its peak spontaneously, falling temporarily to a potential less hyperpolarized than at threshold for the response. As long as current is applied there can be oscillatory behavior with sequential rise and subsidence of the polarization, repeating a number of times. Withdrawal of current leads to rapid return of the potential to the resting level and a small, brief depolarization. Associated with the latter, but of longer duration, is an increased conductance whose magnitude and duration increase with the antecedent current. Hyperpolarizing responses of lobster muscle fibers are due to increased membrane resistance caused by hyperpolarizing K inactivation. The oscillatory characteristic of the response is due to a delayed superimposed and prolonged increase in membrane permeability, probably for Na+ and for either K+ or Cl-. The hyperpolarizing responses of other tissues also appear to result from hyperpolarizing K inactivation, on which is superimposed an increased conductance for some other ion or ions.

Resting membrane potentials: a student test of alternate hypotheses.

1995 ◽  
Vol 269 (6) ◽  
pp. S37 ◽  
Author(s):  
C L Thurman
Keyword(s):  
Hypothesis Testing ◽  
Membrane Permeability ◽  
Channel Blocker ◽  
Membrane Potentials ◽  
Membrane Voltage ◽  
K Channel ◽  
Sartorius Muscle ◽  
Student Test ◽  
Physiology Students ◽  
Frog Sartorius

The frog sartorius muscle is a model tissue for demonstrating to physiology students the principles underlying both membrane phenomena and hypothesis testing. Myocytes can be impaled with conventional glass microelectrodes to measure membrane voltage (Vm). Further, Vm is observed as extracellular K+ is altered and a K+ channel blocker is added. After the experiment, students examine the underlying assumptions of the Nernst equilibrium and the Goldman-Hodgkin-Katz equation. They ultimately determine which of the two algorithms best predicts the measured Vm. In addition, students learn micromanipulation and impalement techniques. This experiment facilitates the student's understanding of membrane permeability, ionic gradients, and membrane voltage.

Role of the Na+/K+-ATPase ion pump in male reproduction and embryo development

2017 ◽  
Vol 29 (8) ◽  
pp. 1457 ◽  
Author(s):  
D. R. Câmara ◽  
J. P. Kastelic ◽  
J. C. Thundathil
Keyword(s):  
Embryo Development ◽  
Reproductive Tract ◽  
Biochemical Properties ◽  
Male Reproduction ◽  
Sperm Function ◽  
Ion Pump ◽  
Ion Pumps ◽  
A Cell ◽  
Na Ions

Na+/K+-ATPase was one of the first ion pumps studied because of its importance in maintaining osmotic and ionic balances between intracellular and extracellular environments, through the exchange of three Na+ ions out and two K+ ions into a cell. This enzyme, which comprises two main subunits (α and β), with or without an auxiliary polypeptide (γ), can have specific biochemical properties depending on the expression of associated isoforms (α1β1 and/or α2β1) in the cell. In addition to the importance of Na+/K+-ATPase in ensuring the function of many tissues (e.g. brain, heart and kidney), in the reproductive tract this protein is essential for embryo development because of its roles in blastocoel formation and embryo hatching. In the context of male reproduction, the discovery of a very specific subunit (α4), apparently restricted to male germ cells, only expressed after puberty and able to influence sperm function (e.g. motility and capacitation), opened a remarkable field for further investigations regarding sperm biology. Therefore, the present review focuses on the importance of Na+/K+-ATPase on male reproduction and embryo development.

scholarly journals Potassium transference in Nitella.

1978 ◽  
Vol 72 (2) ◽  
pp. 203-218 ◽  
Author(s):  
T E Ryan ◽  
C E Barr ◽  
J P Zorn
Keyword(s):  
Major Ions ◽  
Membrane Resistance ◽  
Passive Movement ◽  
Equilibrium Potential ◽  
Ion Pump ◽  
Applied Current ◽  
Experimental Conditions ◽  
Electrochemical Equilibrium ◽  
Passive Model ◽  
Current Shunt

Transmembrane movements of K+ and Cl- were studied under a variety of experimental conditions. Potassium was found to carry more than 50% of an externally applied inward positive current. The increase in K+ influx was much greater than that predicted by the purely passive model. The increase in Cl- efflux accounted for less than 10% of the applied current, in agreement with the value predicted for passive movement. 2,4-Dinitrophenol (DNP) caused an 80% reduction in K+ transference and a corresponding increase in the measured electrical resistance of the membrane. DNP also reduced the isotopically measured resting K+ influx and caused a substantial increase in both Cl- influx and efflux. Lowering of the pH from 5.7 to 4.7 also reduced the net K+ influx but without drastically altering the membrane resistance. It appears the major portion of an externally applied current does not travel through passive channels, but rather is shunted through a different membrane component. In conjunction with evidence previously establishing the H+ pump as the primary ion pump in Nitella, the data presented here are consistent with a K+/H+ exchange mechanism which can account for the observed net K+ accumulation and maintenance of the membrane potential above the electrochemical equilibrium potential of the major ions. This mechanism appears to be a likely candidate for the current shunt.

The active transport of ions in plant cells

1970 ◽  
Vol 3 (3) ◽  
pp. 251-294 ◽  
Author(s):  
E. A. C. MacRobbie
Keyword(s):  
Active Transport ◽  
Experimental Work ◽  
Higher Plants ◽  
Plant Cells ◽  
Transport Processes ◽  
Ion Pump ◽  
Higher Plant ◽  
Active Transport Of Ions ◽  
Wide Range ◽  
Transport Of Ions

In a recent review of the transport of salts and water across multicellular secretory tissues in animals (Keynes, 1969), a summary was given of the various types of active transport of ions necessary to explain the experimental observations in a very wide range of tissues, and five basic types of ion pump were discussed. The question of whether plants and animals have any common mechanisms for the transport of salts and water was specifically excluded. The original aim of the present review was to survey the types of ion pump found in plant cells and tissues, and to compare these with those found in animals. Its aims narrowed very considerably in writing. It now reviews ion transport processes in giant algal cells, and tries to assess progress towards understanding the mechanisms involved. It indicates the existence of similar ion transports in higher plant cells, but it does not present a complete review of the experimental work on higher plants.

scholarly journals The cardiac Na+/K+ ATPase: An updated, thermodynamically consistent model

2020 ◽  
Author(s):  
Michael Pan ◽  
Peter J. Gawthrop ◽  
Joseph Cursons ◽  
Kenneth Tran ◽  
Edmund J. Crampin
Keyword(s):  
Cardiac Electrophysiology ◽  
Extracellular Potassium ◽  
Potassium Accumulation ◽  
Pumping Rate ◽  
Matlab Code ◽  
Consistent Model ◽  
Wide Range ◽  
Original Manuscript ◽  
Metabolite Concentrations ◽  
Cellular Energetics

The Na+/K+ATPase is an essential component of cardiac electrophysiology, maintaining physiological Na+ and K+ concentrations over successive heart beats. Terkildsen et al. (2007) developed a model of the ventricular myocyte Na+/K+ ATPase to study extracellular potassium accumulation during ischaemia, demonstrating the ability to recapitulate a wide range of experimental data, but unfortunately there was no archived code associated with the original manuscript. Here we detail an updated version of the model and provide CellML and MATLAB code to ensure reproducibility and reusability. We note some errors within the original formulation which have been corrected to ensure that the model is thermodynamically consistent, and although this required some reparameterisation, the resulting model still provides a good fit to experimental measurements that demonstrate the dependence of Na+/K+ ATPase pumping rate upon membrane voltage and metabolite concentrations. To demonstrate thermodynamic consistency we also developed a bond graph version of the model. We hope that these models will be useful for community efforts to assemble a whole-cell cardiomyocyte model which facilitates the investigation of cellular energetics.

scholarly journals An intracellular pathway controlled by the N-terminus of the pump subunit inhibits the bacterial KdpFABC ion pump in high K+ conditions

2021 ◽  
Author(s):  
Himanshu Khandelia ◽  
David Stokes ◽  
Bjørn Panyella Pedersen ◽  
Vikas Dubey
Keyword(s):  
Binding Site ◽  
Chemical Potential ◽  
Transmembrane Protein ◽  
Ion Binding ◽  
Ion Pump ◽  
High K ◽  
N Terminus ◽  
P Type ◽  
Intracellular Pathway ◽  
External K

AbstractThe heterotetrameric bacterial KdpFABC transmembrane protein complex is an ion channel-pump hybrid that consumes ATP to import K+ against its transmembrane chemical potential gradient in low external K+ environments. The KdpB ion-pump subunit of KdpFABC is a P-type ATPase, and catalyses ATP hydrolysis. Under high external K+ conditions, K+ can diffuse into the cells through passive ion channels. KdpFABC must therefore be inhibited in high K+ conditions to conserve cellular ATP. Inhibition is thought to occur via unusual phosphorylation of residue Ser162 of the TGES motif of the cytoplasmic A domain. It is proposed that phosphorylation most likely traps KdpB in an inactive E1-P like conformation, but the molecular mechanism of phosphorylation-mediated inhibition and the allosteric links between phosphorylation on the A domain and the inactivation of the pump remain unknown. Here, we employ molecular dynamics (MD) simulations of the dephosphorylated and phosphorylated versions of KdpFABC to demonstrate that phosphorylated KdpB is trapped in a conformation where the ion-binding site is hydrated by an intracellular pathway between transmembrane helices M1 and M2 which opens in response to the rearrangement of cytoplasmic domains resulting from phosphorylation. Cytoplasmic access of water to the ion-binding site is accompanied by a remarkable loss of secondary structure of the KdpB N-terminus and disruption of a key salt bridge between Glu87 in the A domain and Arg212 in the P domain. Our results provide the molecular basis of a unique mechanism of regulation amongst P-type ATPases, and suggest that the N-terminus has a significant role to play in the conformational cycle and regulation of KdpFABC

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