© 1998 by European Society of Cardiology
Copyright © 1998, European Society of Cardiology
Regional differences in the delayed rectifier current (IKr and IKs) contribute to the differences in action potential duration in basal left ventricular myocytes in guinea-pig
aDepartment of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
bDepartment of Cardiology, The London Chest Hospital, Bonner Road, London, UK
* Corresponding author. Tel.: +44 (1865) 22 01 33; Fax: +44 (1865) 22 19 77.
Objective: To compare the properties of single myocytes isolated from different layers of the basal region of the left ventricle and to test the hypothesis that differences in the delayed rectifier current (IK) contribute to regional differences in action potential duration. Methods: Myocytes were isolated from basal sub-endocardial, mid-myocardial and sub-epicardial layers of the guinea-pig left ventricle. Membrane voltage and current were measured using the switch-clamp technique. Results: Mean action potential duration measured at 90% repolarisation (APD90) was longer in sub-endocardial myocytes than in mid-myocardial and sub-epicardial myocytes [APD90 ms at 0.2 Hz: sub-endocardial 292±12 (n=40), mid-myocardial 243±8 (n=42) and sub-epicardial 227±9 (n=36), P<0.001, analysis of variance (ANOVA)]. The APD–rate relationship (stimulation frequencies 2, 1, 0.2 and 0.017 Hz) was steeper in sub-endocardial than in mid-myocardial or sub-epicardial myocytes (P<0.001, ANOVA). The density of IK was greater in mid-myocardial (4.05±0.09 pA pF–1) and sub-epicardial (3.90±0.41 pA pF–1) than in sub-endocardial myocytes (2.74±0.27 pA pF–1, P<0.01 ANOVA). The rapidly-activating (IKr) and slowly-activating (IKs) components of IK were significantly smaller in sub-endocardial than in mid-myocardial or sub-epicardial myocytes. D,L-Sotalol-induced prolongation of APD90 was similar in the three regions studied. Conclusions: There are significant transmural gradients in the electrophysiological properties of myocytes isolated from the base of the left ventricular free wall in guinea-pig. Sub-endocardial myocytes had a longer APD90 attributable in part to a significantly smaller IK density. We have been unable to identify M cells in the guinea-pig left ventricular free wall.
KEYWORDS Heart; Electrophysiology; Action potential duration; Ventricular myocytes; Guinea-pig; Potassium current; Antiarrhythmic agents
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  G. Michael, L. Xiao, X.-Y. Qi, D. Dobrev, and S. Nattel Remodelling of cardiac repolarization: how homeostatic responses can lead to arrhythmogenesis Cardiovasc Res, February 15, 2009; 81(3): 491 - 499. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. J.D. Boukens, V. M. Christoffels, R. Coronel, and A. F.M. Moorman Developmental Basis for Electrophysiological Heterogeneity in the Ventricular and Outflow Tract Myocardium As a Substrate for Life-Threatening Ventricular Arrhythmias Circ. Res., January 2, 2009; 104(1): 19 - 31. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Sun and H.-S. Wang Role of the transient outward current (Ito) in shaping canine ventricular action potential - a dynamic clamp study J. Physiol., April 15, 2005; 564(2): 411 - 419. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H.-S. Wang and I. S Cohen Calcium channel heterogeneity in canine left ventricular myocytes J. Physiol., March 15, 2003; 547(3): 825 - 833. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M Lei, H Honjo, I Kodama, and M R Boyett Heterogeneous expression of the delayed-rectifier K+ currents iK,r and iK,s in rabbit sinoatrial node cells J. Physiol., September 15, 2001; 535(3): 703 - 714. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M Nerbonne Molecular basis of functional voltage-gated K+ channel diversity in the mammalian myocardium J. Physiol., June 1, 2000; 525(2): 285 - 298. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Varro, B. Balati, N. Iost, J. Takacs, L. Virag, D. A Lathrop, L. Csaba, L. Talosi, and J. G. Papp The role of the delayed rectifier component IKs in dog ventricular muscle and Purkinje fibre repolarization J. Physiol., February 15, 2000; 523(1): 67 - 81. [Abstract] [Full Text] [PDF]
|
|