Role of action potential configuration and the contribution of Ca 2+ and K+ currents to isoprenaline-induced changes in canine ventricular cells

N. Szentandrássy, V. Farkas, L. Bárándi, B. Hegyi, F. Ruzsnavszky, B. Horváth, T. Bányász, J. Magyar, I. Márton, P. Nánási

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Background And Purpose Although isoprenaline (ISO) is known to activate several ion currents in mammalian myocardium, little is known about the role of action potential morphology in the ISO-induced changes in ion currents. Therefore, the effects of ISO on action potential configuration, L-type Ca 2+ current (ICa), slow delayed rectifier K+ current (IKs) and fast delayed rectifier K+ current (IKr) were studied and compared in a frequency-dependent manner using canine isolated ventricular myocytes from various transmural locations. Experimental Approach Action potentials were recorded with conventional sharp microelectrodes; ion currents were measured using conventional and action potential voltage clamp techniques. Key Results In myocytes displaying a spike-and-dome action potential configuration (epicardial and midmyocardial cells), ISO caused reversible shortening of action potentials accompanied by elevation of the plateau. ISO-induced action potential shortening was absent in endocardial cells and in myocytes pretreated with 4-aminopyridine. Application of the IKr blocker E-4031 failed to modify the ISO effect, while action potentials were lengthened by ISO in the presence of the IKs blocker HMR-1556. Both action potential shortening and elevation of the plateau were prevented by pretreatment with the ICa blocker nisoldipine. Action potential voltage clamp experiments revealed a prominent slowly inactivating ICa followed by a rise in IKs, both currents increased with increasing the cycle length. Conclusions And Implications The effect of ISO in canine ventricular cells depends critically on action potential configuration, and the ISO-induced activation of IKs- but not I Kr- may be responsible for the observed shortening of action potentials.

Original languageEnglish
Pages (from-to)599-611
Number of pages13
JournalBritish Journal of Pharmacology
Volume167
Issue number3
DOIs
Publication statusPublished - Oct 2012

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Isoproterenol
Action Potentials
Canidae
Muscle Cells
Ions
Nisoldipine
4-Aminopyridine
Microelectrodes
Patch-Clamp Techniques
Myocardium

Keywords

  • β-adrenergic activation
  • action potential configuration
  • calcium current
  • dog myocytes
  • isoprenaline
  • potassium currents
  • ventricular repolarization

ASJC Scopus subject areas

  • Pharmacology

Cite this

Role of action potential configuration and the contribution of Ca 2+ and K+ currents to isoprenaline-induced changes in canine ventricular cells. / Szentandrássy, N.; Farkas, V.; Bárándi, L.; Hegyi, B.; Ruzsnavszky, F.; Horváth, B.; Bányász, T.; Magyar, J.; Márton, I.; Nánási, P.

In: British Journal of Pharmacology, Vol. 167, No. 3, 10.2012, p. 599-611.

Research output: Contribution to journalArticle

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abstract = "Background And Purpose Although isoprenaline (ISO) is known to activate several ion currents in mammalian myocardium, little is known about the role of action potential morphology in the ISO-induced changes in ion currents. Therefore, the effects of ISO on action potential configuration, L-type Ca 2+ current (ICa), slow delayed rectifier K+ current (IKs) and fast delayed rectifier K+ current (IKr) were studied and compared in a frequency-dependent manner using canine isolated ventricular myocytes from various transmural locations. Experimental Approach Action potentials were recorded with conventional sharp microelectrodes; ion currents were measured using conventional and action potential voltage clamp techniques. Key Results In myocytes displaying a spike-and-dome action potential configuration (epicardial and midmyocardial cells), ISO caused reversible shortening of action potentials accompanied by elevation of the plateau. ISO-induced action potential shortening was absent in endocardial cells and in myocytes pretreated with 4-aminopyridine. Application of the IKr blocker E-4031 failed to modify the ISO effect, while action potentials were lengthened by ISO in the presence of the IKs blocker HMR-1556. Both action potential shortening and elevation of the plateau were prevented by pretreatment with the ICa blocker nisoldipine. Action potential voltage clamp experiments revealed a prominent slowly inactivating ICa followed by a rise in IKs, both currents increased with increasing the cycle length. Conclusions And Implications The effect of ISO in canine ventricular cells depends critically on action potential configuration, and the ISO-induced activation of IKs- but not I Kr- may be responsible for the observed shortening of action potentials.",
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AU - Szentandrássy, N.

AU - Farkas, V.

AU - Bárándi, L.

AU - Hegyi, B.

AU - Ruzsnavszky, F.

AU - Horváth, B.

AU - Bányász, T.

AU - Magyar, J.

AU - Márton, I.

AU - Nánási, P.

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N2 - Background And Purpose Although isoprenaline (ISO) is known to activate several ion currents in mammalian myocardium, little is known about the role of action potential morphology in the ISO-induced changes in ion currents. Therefore, the effects of ISO on action potential configuration, L-type Ca 2+ current (ICa), slow delayed rectifier K+ current (IKs) and fast delayed rectifier K+ current (IKr) were studied and compared in a frequency-dependent manner using canine isolated ventricular myocytes from various transmural locations. Experimental Approach Action potentials were recorded with conventional sharp microelectrodes; ion currents were measured using conventional and action potential voltage clamp techniques. Key Results In myocytes displaying a spike-and-dome action potential configuration (epicardial and midmyocardial cells), ISO caused reversible shortening of action potentials accompanied by elevation of the plateau. ISO-induced action potential shortening was absent in endocardial cells and in myocytes pretreated with 4-aminopyridine. Application of the IKr blocker E-4031 failed to modify the ISO effect, while action potentials were lengthened by ISO in the presence of the IKs blocker HMR-1556. Both action potential shortening and elevation of the plateau were prevented by pretreatment with the ICa blocker nisoldipine. Action potential voltage clamp experiments revealed a prominent slowly inactivating ICa followed by a rise in IKs, both currents increased with increasing the cycle length. Conclusions And Implications The effect of ISO in canine ventricular cells depends critically on action potential configuration, and the ISO-induced activation of IKs- but not I Kr- may be responsible for the observed shortening of action potentials.

AB - Background And Purpose Although isoprenaline (ISO) is known to activate several ion currents in mammalian myocardium, little is known about the role of action potential morphology in the ISO-induced changes in ion currents. Therefore, the effects of ISO on action potential configuration, L-type Ca 2+ current (ICa), slow delayed rectifier K+ current (IKs) and fast delayed rectifier K+ current (IKr) were studied and compared in a frequency-dependent manner using canine isolated ventricular myocytes from various transmural locations. Experimental Approach Action potentials were recorded with conventional sharp microelectrodes; ion currents were measured using conventional and action potential voltage clamp techniques. Key Results In myocytes displaying a spike-and-dome action potential configuration (epicardial and midmyocardial cells), ISO caused reversible shortening of action potentials accompanied by elevation of the plateau. ISO-induced action potential shortening was absent in endocardial cells and in myocytes pretreated with 4-aminopyridine. Application of the IKr blocker E-4031 failed to modify the ISO effect, while action potentials were lengthened by ISO in the presence of the IKs blocker HMR-1556. Both action potential shortening and elevation of the plateau were prevented by pretreatment with the ICa blocker nisoldipine. Action potential voltage clamp experiments revealed a prominent slowly inactivating ICa followed by a rise in IKs, both currents increased with increasing the cycle length. Conclusions And Implications The effect of ISO in canine ventricular cells depends critically on action potential configuration, and the ISO-induced activation of IKs- but not I Kr- may be responsible for the observed shortening of action potentials.

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KW - isoprenaline

KW - potassium currents

KW - ventricular repolarization

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