Electrogenic properties of the Na,K pump

Apell, Hans-Jürgen

doi:10.1007/bf01869466

Cited by 77 publications

(35 citation statements)

References 80 publications

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“…In addition, the kinetics of the Na+-K+-pump are voltage-dependent and increase when Vm becomes less negative (Apell, 1989). Experimentally we found an instantaneous depolarization of Vm in low K' as well as in control solution, on addition of ouabain to the perfusion buffer.…”

Section: Discussionmentioning

confidence: 64%

Modulation of the isoprenaline‐induced membrane hyperpolarization of mouse skeletal muscle cells

Mil

Kerkhof

Heukelom

1995

British J Pharmacology

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1 The hyperpolarization of the resting membrane potential, V., induced by isoprenaline in the lumbrical muscle fibres of the mouse, was investigated by use of intracellular microelectrodes.2 In normal Krebs-Henseleit solution (potassium concentration: K+= 5.7 mM, 'control'), V. was -74.0±0.2 mV; lowering K+ to 0.76 mM ('low K'7) resulted in either a hyperpolarization (VM -95.7± 2.9 mV), or a depolarization (Vm= -52.0± 0.3 mV). When Vm hyperpolarized after switching to low K', the addition of isoprenaline resulted in increased hyperpolarization Vm: AVm=-16.3 + 3.2 mV to a final Vm=-110.1I±3.4 mV. Adding iso-prenaline when Vm depolarized in low K+, leads to a hyperpolarization of either by -11.6 ± 0.5 mV to -63.6+0.8 mV or by -51.7+2.7 mV to -106.9±3.9 mV. 5 Ouabain (0.1 to 1 mM) did not suppress the hyperpolarization by isoprenaline in 5.7 mM K + (AVm=-6.7±0.4 mV) or the hyperpolarization of the depolarized cells in low K + (AVm= 9.7 ±1.5 mV). 6The hyperpolarization is a logarithmically decreasing function of K + in the range between 2 and 20 mM (12 mV/decade). 7 IBMX and 8Br-cyclic AMP mimicked the response to isoprenaline whereas forskolin (FSK) induced in low K + a hyperpolarization of -7.0±0.7 mV that could be augmented by addition of isoprenaline (AVm -8.2± 1.8 mV). 8In control and low K+, Ba2`(0.6 mM) inhibited the hyperpolarization induced by isoprenaline, IBMX or 8Br-cyclic AMP. Other blockers of the potassium conductance such as TEA (5 mM) and apamin (0.4 riM) had no effect. 9 We conclude that in the lumbrical muscle of the mouse the isoprenaline-induced hyperpolarization is primarily due to an increase in potassium permeability.

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Section: Discussionmentioning

confidence: 64%

Modulation of the isoprenaline‐induced membrane hyperpolarization of mouse skeletal muscle cells

Mil

Kerkhof

Heukelom

1995

British J Pharmacology

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“…This property of the ion pump is called electrogenicity [55]. An effective way to investigate ion transport is the detection of charge movements in the course of the transport process [2,18,55,75]. Because of the Ping-Pong mechanism it is possible to study separately the Na + -and K + -transport pathways and the associated charge movements.…”

Section: Functional Properties With Structural Implicationsmentioning

confidence: 99%

Functional Properties of Na,K-ATPase, and Their Structural Implications, as Detected with Biophysical Techniques

Apell

Karlish

2001

Journal of Membrane Biology

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Abstract.A full understanding of the molecular mechanism of ion transport and energetics of the Na,K-ATPase will require both structural and functional data. During recent years biophysical methods have provided a number of important pieces of information on ion binding and release and the charge transfer process. This allows the formulation of kinetic models of the transport process. Although a breakthrough has not been obtained due to the lack of detailed knowledge on the threedimensional structure with a resolution high enough to identify the ion-binding sites and the transport pathway, the functional information has structural implications that create constraints on possible mechanisms of active transport. Here we describe briefly contributions of some biophysical methods to our conceptual understanding of the ion transport process.

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“…In principle, the ions could be moved through the interior of the protein dielectric to a certain extent at each of these steps; however, recent investigations revealed that a charge movement occurred mainly during the ion binding and release steps (Apell, Schneeberger & Sokolov, 1998;Butscher, Roudna & Apell, 1999;Apell & Karlish, 2001). Those reaction steps are termed`e lctrogenic'' (LaÈ uger & Apell, 1989;Apell, 1989). To detect and to analyze such reaction steps, experimental techniques are necessary, which allow a resolution of the charge movement in time and amplitude.…”

Section: Introductionmentioning

confidence: 99%

Detection of Charge Movements in Ion Pumps by a Family of Styryl Dyes

Pedersen

Roudná

Beutner

et al. 2002

Journal of Membrane Biology

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Abstract. A family of¯uorescent styryl dyes was synthesized to apply them as probes that monitor the ion-translocating activity of the Na,K-ATPase and the SR Ca-ATPase, similar to the widely used dye RH421. All dyes had the same chromophore but they di ered in the length of the spacer between chromophore and polar head, an isothiocyanate group, and in the lengths of the two identical acyl chains, which form the tail of the dye molecules. A number of substrate-dependent partial reactions of both P-type ATPases a ected the¯uorescence intensity, and the magnitude of the¯uorescence changes was used to characterize the usefulness of the dyes for further application. The experimental results indicate that electrochromy is the major mechanism of these dyes. While in the case of the Na,K-ATPase a single dye, 5QITC, showed larger¯uorescence changes than all others, in the case of the SR Ca-ATPase all dyes tested were almost equal in their¯uorescence responses. This prominent di erence is interpreted as a hint that the position of the ion binding sites in both ion pumps may di er signi®cantly despite their otherwise closely related structural features. Quench experiments with spin-labeled lipids in various positions of their fatty acids were used to gain information on the depth of the chromophore of the di erent dyes within the membrane dielectric, however, the spatial resolution was so poor that only qualitative information on the position of the chromophore in the lipid phase could be obtained.

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Electrogenic properties of the Na,K pump

Cited by 77 publications

References 80 publications

Modulation of the isoprenaline‐induced membrane hyperpolarization of mouse skeletal muscle cells

Modulation of the isoprenaline‐induced membrane hyperpolarization of mouse skeletal muscle cells

Functional Properties of Na,K-ATPase, and Their Structural Implications, as Detected with Biophysical Techniques

Detection of Charge Movements in Ion Pumps by a Family of Styryl Dyes

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