Active Transport Of Potassium Research Articles

The effect of sheep anti‐L and certain cattle S‐system reagents on active potassium transport in sheep and cattle red blood cells

SummaryCertain anti‐sheep L antisera stimulated active potassium transport in cattle red cells. All cattle red cells tested (red cells from 21 Jersey cows) which had an internal K level of less than 70 mmol/1 were stimulated but those with more than 75 mmol/1 of K (red cells from 7 Jersey cows) were not stimulated. Cattle S‐system reagents and isoimmune cattle sera produced by injecting red cells of low‐potassium type into cows with cells of high‐potassium type failed to stimulate active potassium transport in either cattle or sheep red cells.

Isolation and characterization of the components of the sodium pump.

A satisfactory understanding of the functions of the sodium pump, the system responsible for the active transport of sodium and potassium, require the isolation and characterization of its protein and lipid components which are integrated in the structure of the cell membrane. The enzyme system (Na++ K+)-ATPase, is located in membrane fragments and behaves in the test tube like the transport system in the intact cell membrane (Skou,1957) Purified preparations of this enzyme will contain some, if not all, of the components of the sodium pump.

Sodium and Potassium in Human Red Cells Variations among Centrifuged Cells

Separation of human red cells in fractions of different densities was obtained by centrifugation. Prior to the determination of red cell sodium, potassium, and water, trapped extracellular sodium was washed off, using an isotonic sodium-free solution. This method is described in some detail. High density cells had lost potassium and water. Potassium was lost in excess leading to a decrease in cellular potassium concentration. The cellular sodium content was not influenced by cell density, but as a consequence of the water loss, the sodium concentration was increased in the high density cells. While the density-related changes were dominated by the cellular loss of potassium and water, the changes related to digoxin treatment and to hypokalaemia were characterized by an equimolar increase, respectively decrease, in red cell sodium and potassium concentrations (density unchanged); the digoxin-and hypokalaemia-related changes were evenly distributed on the different density fractions and thus independent of cell density. Provided that the high density cells are stable cells in steady state, an increase in potassium permeability combined with an inhibition of active sodium and potassium transport might explain the observed changes in red cell sodium and potassium in the high density cells.

Combined Effects of Digitalis Therapy and of Plasma Bicarbonate on Human Red Cell Sodium and Potassium

Erythrocyte sodium and potassium were studied in 28 patients treated with digitalis glycosides. Red cell sodium increased when digitalis therapy was initiated, and fell to normal when digitalis therapy was stopped. The degree of intracellular sodium accumulation was dependent on plasma bicarbonate concentration. The combination of alkalosis and digitalis therapy may lead to an exceedingly high sodium content of the red cells. The findings are explained by the inhibitory effect of digitalis glycosides on active sodium transport and of the ability of bicarbonate to increase passive sodium permeability. No systematic changes of red cell potassium occurred in this material, probably because the inhibitory effect of digitalis on active potassium transport is counteracted by the previously described stimulatory effect of increased intracellular sodium on the same transport mechanism.

Communication to the editors stimulation of active potassium transport in LK sheep red cells by monovalent fragments of anti-L antibody

Communication to the editors stimulation of active potassium transport in LK sheep red cells by monovalent fragments of anti-L antibody

Communication to the editors stimulation of active potassium transport in LK sheep red cells by monovalent fragments of anti-L antibody

Communication to the editors stimulation of active potassium transport in LK sheep red cells by monovalent fragments of anti-L antibody

Fluid secretion by in vitro preparations of the Malpighian tubules of the desert locust Schistocerca gregaria

In vitro preparations of locust Malpighian tubules can conveniently be made by a new technique in which the alimentary canal to which the tubules attach is removed from the insect and set up in Ringer's solution under liquid paraffin. Such Malpighian tubules will secrete a fluid iso-osmotic to the bathing fluid at a steady rate of about 1 to 2 nl min −1 for some hours. The secreted fluid is rich in potassium ions, the lumen is at a potential positive to that of the bathing solution, and the rate of secretion can be controlled by changing the potassium concentration of the bathing fluid. It seems likely, therefore, that an active transport of potassium drives secretion ny locust Malpighian tubules. The secreted fluid contains an elevated concentration of phosphate ions. The Malpighian tubules will secrete at a high rate in a chloride-free phosphate-based solution. The rate of fluid secretion can be increased by treatment with cyclic AMP but 5-hydroxytryptamine has no such effect.

Active transport of potassium by the giant neuron of the aplysia abdominal ganglion.

We measured the internal potassium activity, a(i) (K), and membrane potential, E(m), simultaneously in 111 R2 giant neurons of Aplysia californica. a(i) (K) was 165.3 +/- 3.4 mM, E(m) was -47.8 +/- 0.9 mv, and E(K) calculated using the Nernst equation was -76.9 +/- 0.05 mv. Such values were maintained for as long as 6 hr of continuous recording in untreated cells, a(i) (K) fell exponentially after the following treatments: cooling to 0.5 degrees -4 degrees C, ouabain, zero external potassium, 2,4-dinitrophenol, and cyanide. The effects of cooling and zero potassium were reversible. Potassium permeability was calculated from net potassium flux using the constant field equation and ranged from 2.6 to 18.5 x 10(-8) cm/sec. We conclude that potassium is actively transported into this neuron against a 30-40 mv electrochemical gradient.

Hydrogen ion role in active transport of potassium and sodium through neuron membranes in the snail Helix pomatia.

The Na and K flux along the concentration gradients and the active transport of these ions through the neuron membrane of the snailHelix pomatia were investigated as functions of pH of the medium by Conway's method (1, 2) of loading cells with Na ions in the cold followed by restoration of the ionic composition by incubation at room temperature. The pH-maximum of the ion migration rates along concentration gradients was in the acid region for Na flux and in the neutral or weakly alkaline region for K. Hydrogen has an inhibitory effect on active ion transport. Analysis of the results by the Lineweaver-Burk method showed that the inhibition of the K influx is competitive, and that of the Na efflux noncompetitive.

Potential-dependent membrane current during the active transport of ions in snail neurones.

1. The membrane current caused by the iontophoretic injection of sodium into giant neurones of the snail Helix pomatia was investigated under a long lasting voltage clamp. The inhibition of this current by ouabain (10(-4) M) and by cooling to + 7 degrees C confirmed its link with the active transport of ions. Therefore this current is called the pump current.2. Over the range of membrane potential -40 to -100 mV the changes in the steady current-voltage curves caused by the pump current development were investigated. The pump current was found to be potential-dependent. It decreased with increasing hyperpolarization of the neurone.3. With large hyperpolarizations the current-voltage curves obtained before the sodium injection and after eliciting the pump current coincided with each other. An increase in the membrane conductance was observed over the range of membrane potential corresponding to the pump current display.4. The applied sodium injections did not cause any marked changes in the passive permeability of the membrane. This fact made it possible to measure the charge transferred across the membrane during operation of the pump current. Unlike previous data, the ratio of this value to the charge used to inject sodium into the neurone appeared to be a variable.5. When the preparation was cooled to + 11 degrees C, and also during the first few minutes after the application of a potassium-free solution, both the pump current and the membrane potential at which it disappeared could increase.6. The pump current measurements during a number of transitions from one fixed level of the membrane potential to another showed that the current did not depend upon the potential at which it developed before each transition.7. The data presented allow the suggestion that the potential dependence of the pump current is determined by the changes in the rate of active transport of potassium, while the rate of active transport of sodium remains constant.

Active transport of potassium and chloride in an identifiable molluscan neuron.

Direct measurements of intracellular K(+) and Cl(-)activities before and after blockage of cellular metabolic processes indicate that K(+) is actively transported inwardly and Cl(-)is actively transported outwardly from the giant cell of the abdominal ganglion of Aplysia. The rewarming of cells that have been cooled to 1 degrees +/- 1 degrees C causes K(+) to be taken up and Cl(-) to be extruded against electrochemical gradients.

Active Transport of α-Aminoisobutyric Acid by the Isolated Midgut of Hyalophora Cecropia

ABSTRACT The α-aminoisobutyric acid flux from lumen to blood of the isolated Cecropia midgut is around 17 μmole/h, while the amino acid flux in the opposite direction is on average 0·3 μmole/h. The amino acid uptake is inhibited by lack of oxygen. It is suggested that the amino acid transport from lumen to blood is an active process. The amino acid uptake is inhibited by short-circuiting the midgut potential, indicating that there is no direct correlation between the active transport of potassium and the uptake of the amino acid by the midgut.

Adenosine Triphosphatase and Active Cation Transport in Red Blood Cell Membranes

Most cells are capable of active transport of sodium and potassium across the cell membrane. The human red blood cell is one of the best studied systems with regard to the characteristics and mechanism of active cation transport. A membrane-associated enzyme, adenosine triphosphatase activated by Na and K (Na,K-ATPase), appears to be identical with the Na-K pump. The evidence includes similar kinetic properties and responses to cardiac glycosides of the pump and Na,-K-ATPase, the spatial asymmetry of activation of both pump and enzyme by K and Na, and synthesis of ATP mediated by the pump working in reverse. The energy-dependent transfer of Na and K through the membrane appears to be associated with the following reactions of Na,-K-ATPase: Na-dependent phosphorylation of the enzyme; conversion to a second form of phosphorylated enzyme; and K-dependent release of phosphate.

Biogenesis of mitochondria. 20. The effects of altered membrane lipid composition on mitochondrial oxidative phosphorylation in Saccharomyces cerevisiae.

1. The lipid composition of mitochondria isolated from a fatty acid desaturase mutant ofSaccharomyces cerevisiae may be extensively manipulated by growing the organism on defined supplements of unsaturated fatty acid (UFA). 2. The fatty acid composition of the mitochondrial lipids closely follows that of the whole cells from which the mitochondria are isolated. UFA-depleted mitochondria contain normal levels of sterols, neutral lipids and total phospholipids, but have much lower levels of phosphatidyl inositides. 3. UFA-depleted mitochondria possess a full complement of cytochromes, oxidase both NAD-linked and flavoprotein-linked substrates at normal rates, and have levels of succinate and malate dehydrogenases similar to those of UFA-supplemented mitochondria. However, UFA-depletion has a marked effect on the ability of cytochromec to reactivate the NADH oxidase activity of cytochromec-depleted mitochondria. 4. The efficiency of oxidative phosphorylation decreases progressively with the UFA content of the mitochondria, and oxidative phosphorylation is completely lost in mitochondria containing approximately 20% UFA. 5. The incorporation of UFA into the lipids of UFA-depleted mitochondriain vivo results in a recoupling of oxidative phosphorylation. Recoupling is insensitive to both chloramphenicol and cycloheximide, indicating that all the proteins necessary for oxidative phosphorylation are present in UFA-depleted mitochondria, and that the less of oxidative phosphorylation is a purely lipid lesion. 6. ATPase activity is apparently unaffected by UFA-depletion, but32Pi-ATP exchange activity is lost in mitochondria which have been extensively depleted in UFA. 7. Valinomycin stimulates the respiration of UFA-supplemented mitochondria in media containing potassium, but has no effect on the respiration of UFA-depleted mitochondria, suggesting that active transport of potassium is lost as a result of UFA-depletion.

Active sodium and potassium transport in high potassium and low potassium sheep red cells.

The kinetic characteristics of the ouabain-sensitive (Na + K) transport system (pump) of high potassium (HK) and low potassium (LK) sheep red cells have been investigated. In sodium medium, the curve relating pump rate to external K is sigmoid with half maximal stimulation (K(1/2)) occurring at 3 mM for both cell types, the maximum pump rate in HK cells being about four times that in LK cells. In sodium-free media, both HK and LK pumps are adequately described by the Michaelis-Menten equation, but the K(1/2) for HK cells is 0.6 +/- 0.1 mM K, while that for LK is 0.2 +/- 0.05 mM K. When the internal Na and K content of the cells was varied by the PCMBS method, it was found that the pump rate of HK cells showed a gradual increase from zero at very low internal Na to a maximum when internal K was reduced to nearly zero (100% Na). In LK cells, on the other hand, no pump activity was detected if Na constituted less than 70% of the total (Na + K) in the cell. Increasing Na from 70 to nearly 100% of the internal cation composition, however, resulted in an exponential increase in pump rate in these cells to about (1/6) the maximum rate observed in HK cells. While changes in internal composition altered the pump rate at saturating concentrations of external K, it had no effect on the apparent affinity of the pumps for external K. These results lead us to conclude that the individual pump sites in the HK and LK sheep red cell membranes must be different. Moreover, we believe that these data contribute significantly to defining the types of mechanism which can account for the kinetic characteristics of (Na + K) transport in sheep red cells and perhaps in other systems.

Potassium accumulation by bulk prepared neuronal and glial cells.

Abstract— Neuronal and glial cell enriched fractions were prepared by density gradient centrifugation of suspensions from rabbit cerebral cortex. The two cell types were incubated separately in media of extracellular ionic composition. The potassium accumulation was determined from analysis of potassium content of the cells by ultramicro flame photometry. Both neuronal and glial cells were capable of active potassium transport which was inhibited by ouabain (2 × 10−4m). The glial cells could accumulate potassium up to four to five times the concentration of the incubation medium and neurons up to one and a half to two times the medium concentration. The respiration in low potassium media was stimulated 15 per cent for neurons and 85 per cent for glia when potassium was added to a final concentration of 50 mm. The uptake by both neurons and glia showed temperature and sodium dependence. There was a definite magnesium requirement for the potassium uptake, particularly demonstrable for glial cells. Calcium inhibited potassium uptake by glia but stimulated slightly that by neurons.

Effect of amphotericin B on the frog skin in vitro. Evidence for outward active potassium transport across the epithelium.

AbstractIt is shown that amphotericin B (5×10‐5 M) increases the permeability of the frog skin to potassium, chloride and urea. The potassium flux was more strongly increased from the inside to the outside than from the outside to the inside of the skin, whereas the chloride and the urea fluxes were equally enhanced in both directions. The increased potassium flux from the inside to the outside could not be explained by a potassium loss from the cells. It is suggested that a part of the high outward potassium flux was due to an active outwards transport of potassium.

The Nature of the Antibody in Iso-Immune Anti-L Sera Affecting Active Potassium Transport in LK Sheep Red Cells

Abstract The factor in ovine iso-immune L-antiserum that was responsible for stimulation of active K+-transport in LK sheep red cells was found to be an antibody of the IgG1 class. Reduction and alkylation of the anti-L-IgG1 protein abolished its K+-pump stimulatory activity. Treatment with papain to yield univalent Fab fragments substantially reduced stimulatory activity; there was no enhancement from the Fc protein. Bivalent fragments obtained by pepsin digestion, however, were nearly fully active in effecting stimulation of active K+-transport in LK sheep red cells.

Diphenylhydantoin and potassium transport in isolated nerve terminals.

THE ANTIEPILEPTIC ACTION OF DIPHENYLHYDANTOIN (DPH) HAS BEEN EXPLAINED BY TWO DIFFERENT THEORIES: (a) that DPH stimulates the Na-K pump; (b) that DPH specifically blocks the passive translocation of sodium. Since electrophysiological experiments have recently suggested abnormal synaptic mechanisms as the basis for epileptogenic discharges, the action of DPH on K transport within synaptic terminals isolated from "normal" rat brain cortex was examined directly. A rapid filtration technique was used to assess in vitro potassium transport within synaptosomes. In vivo DPH did not significantly change endogenous K content within synaptosomes. With sodium (50 mM) and potassium (10 mM) concentrations optimal for Na-K pump activity, in vivo and in vitro DPH (10(-4) M) had minimal or no effects on total K uptake. DPH stimulated potassium uptake within synaptosomes under two situations: (a) at high sodium (50-100 mM) and low potassium (less than 2 mM) concentrations; (b) when synaptosomes were incubated with ouabain (10(-4) M) 50 mM Na and 10 mM K. In both situations, K was leaking out of synaptic terminals and the enhancement in net K uptake roughly corresponded to the ouabain inhibitable segment. In the absence of ouabain, the stimulatory effects of DPH were not observed when K was 2 mM or higher and when Na was 10 mM or lower. The stimulatory effects of in vitro DPH appeared over a range of concentrations from 10(-4) to 10(-10) M while single intraperitoneal injections of DPH had to be administered for 2 days before its effects were observed on synaptosomal K transport. The present data provided direct evidence for DPH stimulation of active potassium transport within synaptosomes under ionic conditions simulating the depolarized state. At other ionic conditions, DPH had inhibitory or no effects on K uptake. Although the results do not specify whether the effects of DPH on the Na-K pump are direct or indirect, they suggest that the action of DPH depends upon the state of the membrane and the specific ionic environment.

The effect of angiotensin on cation transport by rat kidney cortex slices

1. A study has been made of the effect of angiotensin (10(-12) g/ml.) on active and passive transport of sodium, potassium and water between rat kidney cortex slices and the incubation medium.2. Angiotensin has no effect on the passive uptake of sodium and loss of potassium by slices incubated under conditions which inhibit active transport.3. Active sodium extrusion by slices incubated under aerobic conditions is stimulated, whereas active potassium uptake is inhibited by angiotensin.4. Sodium pump activity is stimulated by angiotensin in the presence of ouabain or in the absence of potassium in the incubation medium, conditions which block the sodium for potassium exchange pump.5. There is a 2 min latent period following the application of angiotensin before a response is observed.6. These findings are discussed in relation to the mechanism of action of angiotensin on kidney sodium and fluid transport processes.