scholarly journals K+ transport in Malpighian tubules of Tenebrio molitor L.: a study of electrochemical gradients and basal K+ uptake mechanisms

2003 ◽  
Vol 206 (6) ◽  
pp. 949-957 ◽  
Author(s):  
U. I. M. Wiehart
Keyword(s):  
Tenebrio Molitor ◽  
Malpighian Tubules ◽  
K Uptake ◽  
K Transport ◽  
Uptake Mechanisms

scholarly journals The Arabidopsis thaliana K+-Uptake Permease 5 (AtKUP5) Contains a Functional Cytosolic Adenylate Cyclase Essential for K+ Transport

2018 ◽  
Vol 9 ◽  
Author(s):  
Inas Al-Younis ◽  
Aloysius Wong ◽  
Fouad Lemtiri-Chlieh ◽  
Sandra Schmöckel ◽  
Mark Tester ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Adenylate Cyclase ◽  
K Uptake ◽  
K Transport

scholarly journals CATION TRANSPORT IN YEAST

1956 ◽  
Vol 39 (5) ◽  
pp. 687-704 ◽  
Author(s):  
Ernest C. Foulkes
Keyword(s):  
Cell Membrane ◽  
Dissociation Constant ◽  
Concentration Gradient ◽  
Cation Transport ◽  
K Uptake ◽  
Present Evidence ◽  
Inhibitor Complex ◽  
Maximum Value ◽  
Low Concentrations ◽  
K Transport

1. The distribution of azide added to suspensions of bakers' yeast was studied under various conditions. The recovery of azide was estimated in the volume of water into which low concentrations of electrolytes can readily diffuse (anion space). Considerable azide disappeared from this anion space. 2. The incomplete recovery of azide in the anion space is due to its uptake by the cells. This uptake occurs against a concentration gradient at 0°C., and is attributed to binding of azide by cell constituents. 3. Confirmatory evidence is presented that one such constituent is the K carrier in the cell membrane. The azide inhibition of K transport is not mediated by inhibition of cytochrome oxidase in the mitochondria. 4. From the amount of combined azide and the experimentally determined dissociation constant of the K carrier-inhibitor complex, the maximum value for the concentration of this carrier is calculated as 0.1 µM/gm. yeast. 5. The addition of glucose and PO4 causes a secondary K uptake which is not azide-sensitive and is clearly distinct from the primary, azide-sensitive mechanism. 6. The existence of a separate carrier responsible for Na extrusion is reconsidered. It is concluded that present evidence does not necessitate the assumption that such a carrier is active in yeast.

Cell volume regulation by skate erythrocytes: role of potassium

1990 ◽  
Vol 258 (5) ◽  
pp. R1217-R1223 ◽  
Author(s):  
K. G. Dickman ◽  
L. Goldstein
Keyword(s):  
Cell Volume ◽  
Phorbol Ester ◽  
Volume Regulation ◽  
Regulatory Volume Decrease ◽  
Cell Volume Regulation ◽  
Disulfonic Acid ◽  
Ionophore A23187 ◽  
K Uptake ◽  
K Transport

The role of K transport during cell volume regulation in response to extracellular osmolality, protein kinase C activation, and cellular Ca was examined in skate (Raja erinacea) red blood cells (RBC). Reduction of medium osmolality from 960 to 660 mosmol/kgH2O had no effect on K uptake or efflux despite a 25% increase in cell volume. Further reduction to 460 mosmol/kgH2O caused K uptake to double and K efflux to triple resulting in net K loss. Net K efflux in 460 mosmol/kgH2O medium was correlated with the presence of a regulatory volume decrease, which was sensitive to the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and insensitive to chloride replacement. K-K exchange was absent in both isotonic and hypotonic media. Treatment with the Ca ionophore A23187 in the presence of Ca had no effect on either cell volume or K efflux in isotonic medium, indicating the absence of Ca-activated K transport. In contrast, phorbol ester treatment caused cell volume, Na content, and proton and K efflux to increase. Consistent with activation of Na-H exchange, phorbol ester effects were inhibited by dimethylamiloride. This study constitutes the first demonstration of volume-sensitive K transport in RBC from the most primitive vertebrate studied to date.

scholarly journals Cation transport in Escherichia coli. IX. Regulation of K transport.

1978 ◽  
Vol 72 (3) ◽  
pp. 283-295 ◽  
Author(s):  
D B Rhoads ◽  
W Epstein
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Cation Transport ◽  
Transport Systems ◽  
Energy Requirements ◽  
Protonmotive Force ◽  
K Uptake ◽  
Kinetics Of ◽  
K Transport ◽  
External K

Kinetics of K exchange in the steady state and of net K uptake after osmotic upshock are reported for the four K transport systems of Escherichia coli: Kdp, TrkA, TrkD, and TrkF. Energy requirements for K exchange are reported for the Kdp and TrkA systems. For each system, kinetics of these two modes of K transport differ from those for net K uptake by K-depleted cells (Rhoads, D. B. F.B. Walters, and W. Epstein. 1976. J. Gen. Physiol. 67:325-341). The TrkA and TrkD systems are inhibited by high intracellular K, the TrkF system is stimulated by intracellular K, whereas the Kdp system is inhibited by external K when intracellular K is high. All four systems mediate net K uptake in response to osmotic upshock. Exchange by the Kdp and TrkA systems requires ATP but is not dependent on the protonmotive force. Energy requirements for the Kdp system are thus identical whether measured as net K uptake or K exchange, whereas the TrkA system differs in that it is dependent on the protonmotive force only for net K uptake. We suggest that in both the Kpd and TrkA systems formation of a phosphorylated intermediate is necessary for all K transport, although exchange transport may not consume energy. The protonmotive-force dependence of the TrkA system is interpreted as a regulatory influence, limiting this system to exchange except when the protonmotive force is high.

scholarly journals Influence of Haemoglobin Conformation, Nitrite and Eicosanoids on K+ Transport Across the Carp Red Blood Cell Membrane

1992 ◽  
Vol 171 (1) ◽  
pp. 349-371 ◽  
Author(s):  
FRANK B. JENSEN
Keyword(s):  
Membrane Potential ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Quaternary Structure ◽  
Large Fraction ◽  
Nordihydroguaiaretic Acid ◽  
K Uptake ◽  
Root Effect ◽  
T State ◽  
K Transport

The regulation of K+ transport across the red blood cell (RBC) membrane by haemoglobin (Hb) conformation was studied in carp, and the K+ transport mechanisms were identified. When a large proportion of Hb in the R quaternary structure was secured by oxygenation of blood at pH8.14, a net RBC K+ efflux was induced, which was accompanied by RBC shrinkage. This K+ efflux was resistant to ouabain and inhibited by furosemide and DIDS and by substitution of NO3− for Cl−, showing it to result from a K+/Cl− cotransport mechanism. Deoxygenation of the RBCs (Hb in T structure) eliminated the Cl−-dependent K+ efflux and resulted in a net K+ uptake via the Na+/K+ pump. These changes were fully reversible. Nitrite-induced methaemoglobin formation in deoxygenated blood, which converts a large fraction of the T structure Hb into an R-like conformation, shifted the K+ uptake to a Cl−-dependent K+ efflux similar to that seen in oxygenated cells. When the allosteric equilibrium between the R and T structures of Hb was gradually shifted towards the T state by decreases in pH, the Cl−-dependent K+ efflux from oxygenated cells decreased. At pH7.52, where the Root effect caused a potent stabilisation of the T state, the K+ efflux was reversed to a net K+ uptake. A similar change was induced in methaemoglobin-containing deoxygenated blood, since low pH also favours a T-like conformation of metHb. The variable K+ fluxes could not be related to changes in membrane potential or pH but were always directly related to the experimental modulation of the relative proportions of R- and T-structure Hb. It is proposed that Hb conformation governs K+ movements via a different binding of T and R structures to integral membrane proteins, and that a large fraction of R-structure Hb triggers the Cl−dependent K+ efflux mechanism. Application of inhibitors and a substrate of prostaglandin and leukotriene synthesis did not influence the K+ efflux from oxygenated erythrocytes. However, a fraction of the K+ efflux from nitrite-treated deoxygenated cells was inhibited by nordihydroguaiaretic acid, suggesting that a slightly larger K+ efflux from these RBCs than from oxygenated RBCs was related to leukotriene production caused by nitrite entry. A much larger influx of nitrite to deoxygenated than to oxygenated RBCs was positively correlated with the distribution ratio of H+ and the membrane potential, supporting the view that nitrite primarily enters the cells via conductive transport. The physiological implications of the results are discussed.

Water vapor absorption in insects

1983 ◽  
Vol 244 (2) ◽  
pp. R187-R192 ◽  
Author(s):  
J. Machin
Keyword(s):  
Water Vapor ◽  
Ion Transport ◽  
Water Transport ◽  
Malpighian Tubules ◽  
Water Vapor Absorption ◽  
Water Flows ◽  
Vapor Absorption ◽  
Tubular Lumen ◽  
Kcl Transport ◽  
Uptake Mechanisms

In common with other animals the principal examples of water transport in insects are to be found in processing food and in excretion. Some insects and other arthropods are able to absorb water vapor using preexisting buccal or rectal structures. This unique exploitation of atmospheric water depends on adequate areas for condensing water vapor and the capacity for considerable "uphill" water transport. All known uptake mechanisms depend on producing fluids of sufficiently low water activity to bring about condensation from a range of environmental humidities. In the best-understood examples (mealworms and their relatives) active KCl transport by the Malpighian tubules generates osmotic pressures sufficient to extract water from activities down to 0.88. A standing gradient model seems to describe the coupling in the tubular lumen between water flows and ion transport. Low water permeabilities and ion transport modulated with flow rate are unusual features of this coupling.

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