Heterogeneity of Sodium Current in Atrial vs Epicardial Ventricular Myocytes of Adult Guinea Pig Hearts

doi:10.1006/jmcc.2002.2053

Journal of Molecular and Cellular Cardiology

Volume 34, Issue 9, September 2002, Pages 1185-1194

https://doi.org/10.1006/jmcc.2002.2053 Get rights and content

Abstract

G.-R. L i, C.-P. L au and A. S hrier. Heterogeneity of Sodium Current in Atrial vs Epicardial Ventricular Myocytes of Adult Guinea Pig Hearts. Journal of Molecular and Cellular Cardiology (2002) 34, 1185–1194. The different sodium channel currents (I_Na) were reported in myocardium, neuron, and skeletal muscles. To study whether I_Na is homogeneous within the heart, we applied whole-cell voltage clamp technique to evaluate fast voltage-gated I_Na in atrial and ventricular myocytes isolated from guinea pig heart. It was found that the density of inward I_Na was 50% greater at −35 mV in atrial (−42.6±2.9 pA/pF) than in ventricular (−27.5±1.8 pA/pF, P<0.01) myocytes. The half activation and inactivation voltages (V_0.5) of I_Na in atrial myocytes were shifted 4.5±0.2 and 9.6±0.3 mV negative to those of ventricular myocytes. Time constants forI_Na activation (τ_m) and inactivation (τ_h) were twice as rapid in atrial as in ventricular myocytes. The τ_m and τ_h were 0.34±0.03 and 1.36±0.07 ms for atrial myocytes, and 0.69±0.05 and 3.27±0.23 ms for ventricular myocytes, respectively. Recovery ofI_Na from inactivation was slower in atrial than in ventricular myocytes, whereas the development of resting state inactivation was more rapid in atrial (τ=67.5±4.3 ms) than in ventricular (152.8±7.5 ms, P<0.01) myocytes. The results reveal marked heterogeneity of I_Na in the density and biophysical properties in atrial and ventricular myocytes, and the study suggests the potential possibility of tissue specific cardiac sodium channel isoforms.

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^f1: Please address all correspondence to: Dr. Gui-Rong Li, L04-55, New Medical Complex, Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong SAR China. Tel: (852)2819-2380; Fax: (852)2855-9730; E-mail:[email protected]

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Regular ArticleHeterogeneity of Sodium Current in Atrial vs Epicardial Ventricular Myocytes of Adult Guinea Pig Hearts

Abstract

J Am Coll Cardiol

Biophys J

Biophys J

Biophys J

J Mol Cell Cardiol

J Am Coll Cardiol

Am J Med

J Biol Chem

J Biol Chem

J Biol Chem

Biochem Biophys Res Commun

Ionic basis of the different action potential configurations of single guinea-pig atrial and ventricular myocytes

J Physiol

Differential responsiveness of atrial and ventricular myocytes to potassium channel openers

J Cardiovasc Pharmacol

Heterogeneity within the ventricular wall. Electrophysiology and pharmacology of epicardial, endocardial, and M cells

Circ Res

Heterogeneity of action potential waveforms and potassium currents in rat ventricle

Cardiovasc Res

Transmural heterogeneity of action potentials and Ito1 in myocytes isolated from the human right ventricle

Am J Physiol

Evidence for the presence of M cells in the guinea pig ventricle

J Cardiovasc Electrophysiol

M cells and transmural heterogeneity of action potential configuration in myocytes from the left ventricular wall of the pig heart

Cardiovasc Res

Determinants of action potential initiation in isolated rabbit atrial and ventricular myocytes

Am J Physiol

Structure and function of voltage-dependent sodium channels: comparison of brain II and cardiac isoforms

Physiol Rev

Two sodium-channel genes in Drosophila: implications for channel diversity

Proc Natl Acad Sci U S A

Differential effects of homologous S4 mutations in human skeletal muscle sodium channels on deactivation gating from open and inactivated states

J Physiol

Electrophysiological characteristics of cloned skeletal and cardiac muscle sodium channels

Am J Physiol

Electrophysiological properties of morphologically distinct cells isolated from the rabbit atrioventricular node

J Physiol

Regular Article
Heterogeneity of Sodium Current in Atrial vs Epicardial Ventricular Myocytes of Adult Guinea Pig Hearts

Transmural heterogeneity of action potentials and I_to1 in myocytes isolated from the human right ventricle