Role of the sodium pump and the background K+ channel in passive K+(Rb+) uptake by isolated cardiac sarcolemmal vesicles

Otero, Angela S.; Szabó, Gábor

doi:10.1007/bf01872327

Cited by 7 publications

(3 citation statements)

References 40 publications

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“…Sarcolemma was purified from bullfrog and beef heart according to the procedures of Otero and Szabo (1988) and Jones (1988), respectively. Specific activity of muscarinic cholinergic binding sites (measured as [3H] quinuclidinyl benzilate binding sites) in sarcolemmal preparations were 6-7 pmol/mg (frog) and 3-4 pmol/mg (beef).…”

Section: Preparationsmentioning

confidence: 99%

Differential effects of pertussis toxin on the muscarinic regulation of Ca2+ and K+ currents in frog cardiac myocytes.

Hanf

Otero

et al. 1994

The Journal of General Physiology

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The ability of acetylcholine (ACh) to inhibit 13-agonist stimulated calcium current was compared to its ability to activate the inwardly rectifying potassium current Ig(ACh) in frog atrial myocytes. As suggested by previous studies, ACh inhibited the calcium current at concentrations (ECs0 = 8 nM) significantly lower than those required for the activation of IK(ACh) (ECs0--101 nM). The pharmacological profiles of the two responses suggest that despite the differences in agonist sensitivity, both are mediated by the same (m~) type of muscarinic receptors. Intracellular application of GDPI3S, an inhibitor of G protein function, completely abolished both responses, implying that both actions of ACh are coupled to effectors by G proteins. In contrast, intracellular application of pertussis toxin (PTX) shifted to higher concentrations (ECs0 = 170 nM) but did not abolish inhibition of the calcium current by ACh even though the block of the IK(ACh) response was complete. Increasingly large PTX concentrations and/or prolonged PTX treatments revealed a limiting, FTX-resistant inhibitory component that appears to be mediated by a FFX-insensitive G protein distinct from that mediating IK(ACh)-For the FIX-sensitive components, the different agonist dependencies of

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Section: Preparationsmentioning

confidence: 99%

Differential effects of pertussis toxin on the muscarinic regulation of Ca2+ and K+ currents in frog cardiac myocytes.

Hanf

Otero

et al. 1994

The Journal of General Physiology

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“…For the determination of antibody effects on the NDP kinase activity of frog cardiac sarcolemma, purified membranes (22) were permeabilized with saponin (2 mg/ml) for 20 min and then incubated on ice with either antibody in 50 l of 75 mM KCl, 5 mM MgCl 2 , 1 mg/ml bovine serum albumin, and 50 mM Tris⅐HCl, pH 7.5. After 1 h, the NDP kinase activity of each mixture was assayed in duplicate or triplicate.…”

mentioning

confidence: 99%

Participation of Nucleoside-diphosphate Kinase in Muscarinic K+ Channel Activation Does Not Involve GTP Formation

Murphy

Otero

1996

Journal of Biological Chemistry

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Agonist-bound muscarinic receptors open atrial K+ channels through a GTP-dependent pathway mediated by the G protein Gk. However, nucleotides other than GTP are also able to support channel activity, even in the absence of agonists. This process was proposed to be mediated by nucleoside-diphosphate (NDP) kinase, which would transfer phosphate from nucleotide triphosphates to the GDP bound to Gk, producing Gk-GTP without the need for receptor-induced GDP-GTP exchange. We examined the effect of antibodies to NDP kinase on the ATP-supported activity of atrial muscarinic K+ channels and the corresponding GIRK1/CIR channels expressed in HEK 293 cells. Inhibitory antibodies reduced ATP-induced channel openings, but this effect displayed an absolute requirement for agonist and was also seen with antibodies that do not inhibit the enzyme. Both types of antibodies also reduced agonist-dependent channel activity in the presence of GTP, ruling out a role for NDP kinase in GDP rephosphorylation. Channel activity was not affected by the antibodies in preparations where ATP-induced muscarinic channels are not under tight receptor control, namely pertussis toxin-treated atrial patches and membranes from cells expressing KACh channel subunits. Thus, participation of NDP kinase in this pathway requires activated receptors and has a function distinct from phosphate transfer between nucleotides.

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“…На данный момент имеются десятки статей по: замещающему действию ионов Rb + на калиевые каналы (см., напр. : [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102] [154,[156][157][158][159][160][161][162][163][164][165] и др. металлов.…”

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Correlational Patch-Clamp Spectrometry of the Ion Channels

Градов¹

2017

Preprint

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Membrane ion channels operate in accordance with the main principles of coordination chemistry. Coordination number is known to determine the ion selectivity of the sodium and potassium channels. there are known both ligand-dependent and ligand-controlled ion channels operating within the supramolecular coordination fixation principles. The channelforming ionophores form the structures which bind cations via coordination bonds leading to the conformational changes with the adjustment of the whole supramolecular architecture providing the ion channel selectivity. Such kind of non-covalent systems underlie the electrogenic membrane functions and the potential-controlled transmembrane ion transfer systems. They can be studied by means of the path-clamp method (i.e. the local membrane potential fixation), such as the «anion clamp», applied together with the analysis of the metal ion coordination geometry with the ion channels. However, such methods are not capable to register the ion channel conformational state in situ -during the ion coordination -with the molecular resolution of the ion channel structure. In this regard there is a need to develop dynamical methods capable of the simultaneous registration of the conformational and metallomic / elementomic coordination parameters and the electrophysiological response to the ion coordination. We propose to develop for this purpose a special kind of spectroscopic systems providing registration of the electrophysiological parameters and the single ion channel response by means of the local potential fixation techniques (patch-clamp / voltageclamp) with the advanced spectral processing and the subsequent data mining, with the simultaneous spectral detection of the ion channel state as a coordination and conformationally labile supramolecular structure, with the final data processing results presented not as the single spectra, but as the spectral correlogram.

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Role of the sodium pump and the background K+ channel in passive K+(Rb+) uptake by isolated cardiac sarcolemmal vesicles

Cited by 7 publications

References 40 publications

Differential effects of pertussis toxin on the muscarinic regulation of Ca2+ and K+ currents in frog cardiac myocytes.

Differential effects of pertussis toxin on the muscarinic regulation of Ca2+ and K+ currents in frog cardiac myocytes.

Participation of Nucleoside-diphosphate Kinase in Muscarinic K+ Channel Activation Does Not Involve GTP Formation

Correlational Patch-Clamp Spectrometry of the Ion Channels

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