Document Detail

Normal regional distribution of membrane current density in rat left ventricle is altered in catecholamine-induced hypertrophy.
MedLine Citation:
PMID:  10533575     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To test the hypothesis that changes in the normal regional distribution of potassium and calcium currents contribute to the different regional changes in action potential duration in isoprenaline-induced hypertrophy in rats. METHODS: Hypertrophy was elicited in rats by seven daily injections of isoprenaline. Left ventricular myocytes were isolated from basal sub-endocardial, basal mid-myocardial and apical sub-epicardial tissue. Membrane currents were measured using the whole-cell patch-clamp technique at 35 +/- 1 degrees C. RESULTS: Cell membrane capacitance was similar in all three groups and was increased by 17% in hypertrophy (P < 0.001, t-test). Changes in the calcium-independent transient outward current (Ito1) density in hypertrophy were different in the three regions (P < 0.05, ANOVA). Ito1 was reduced in sub-epicardial (control, 23.4 +/- 2.0 pA pF-1; hypertrophy, 15.8 +/- 1.5 pA pF-1, P < 0.01 ANOVA) and in mid-myocardial myocytes (control, 24.0 +/- 2.8 pA pF-1; hypertrophy, 13.8 +/- 1.3 pA pF-1, P < 0.01 ANOVA) and was not significantly altered in sub-endocardial myocytes (control, 8.5 +/- 0.7 pA pF-1; hypertrophy, 7.4 +/- 1.8 pA pF-1). Steady-state background current density was reduced in hypertrophy (P < 0.05, ANOVA). The regional difference in steady-state background current in control hearts (P < 0.05, ANOVA) was altered in hypertrophy. Calcium current (ICa) density was similar in the three regions studied in both control and hypertrophied hearts. ICa was reduced in hypertrophy (P < 0.05, ANOVA). CONCLUSION: The normal regional differences in Ito1 are reduced, in steady-state background current are altered and in ICa are unchanged in catecholamine-induced hypertrophy in the rat left ventricle. These data may in part explain the reduction in the normal regional differences in APD observed in hypertrophy.
S M Bryant; S J Shipsey; G Hart
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Cardiovascular research     Volume:  42     ISSN:  0008-6363     ISO Abbreviation:  Cardiovasc. Res.     Publication Date:  1999 May 
Date Detail:
Created Date:  1999-11-04     Completed Date:  1999-11-04     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0077427     Medline TA:  Cardiovasc Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  391-401     Citation Subset:  IM    
Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, UK.
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MeSH Terms
Action Potentials*
Analysis of Variance
Biological Transport, Active*
Calcium / metabolism
Cardiomegaly / metabolism,  physiopathology*
Cardiotonic Agents
Heart / physiopathology*
Ion Transport
Patch-Clamp Techniques
Potassium / metabolism
Rats, Wistar
Reg. No./Substance:
0/Cardiotonic Agents; 7440-09-7/Potassium; 7440-70-2/Calcium; 7683-59-2/Isoproterenol

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