Document Detail

Characterisation of the transient outward K+ current in rabbit sinoatrial node cells.
MedLine Citation:
PMID:  10912454     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To (i) characterise the electrophysiological and pharmacological properties of the transient outward K+ current, I(to), (ii) determine the relationship between the density of I(to) and cell size, and (iii) determine the role of I(to) in electrical activity in rabbit sinoatrial node cells at 35 degrees C. METHODS: Rabbit sinoatrial node cells were studied using whole-cell voltage and current clamp techniques. RESULTS: I(to) showed half activation and inactivation at +11 and -49 mV, respectively. I(to) was blocked by 4-aminopyridine (4-AP) as well as the class I agents, quinidine and flecainide, with EC50 values of 326, 21 and 19 microM, respectively. The densities of the transient and sustained components of 4-AP-sensitive current were significantly correlated with cell capacitance, a measure of cell size, and were greater in cells with a larger capacitance. Block of I(to) by 4-AP affected both the action potential and pacemaker activity of sinoatrial node cells and the effects were greater in cells with a larger capacitance. CONCLUSIONS: I(to) in sinoatrial node cells shows similar electrophysiological and pharmacological properties to I(to) in atrial and ventricular cells. The expression of I(to) in sinoatrial node cells is heterogeneous and differs in large and small cells (likely to be from the periphery and centre of the sinoatrial node, respectively). I(to) plays an important role in action potential configuration and pacemaker activity in sinoatrial node cells, especially in larger cells.
M Lei; H Honjo; I Kodama; M R Boyett
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Cardiovascular research     Volume:  46     ISSN:  0008-6363     ISO Abbreviation:  Cardiovasc. Res.     Publication Date:  2000 Jun 
Date Detail:
Created Date:  2000-09-05     Completed Date:  2000-09-05     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0077427     Medline TA:  Cardiovasc Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  433-41     Citation Subset:  IM    
School of Biomedical Sciences, University of Leeds, UK.
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MeSH Terms
4-Aminopyridine / pharmacology*
Action Potentials / drug effects*
Anti-Arrhythmia Agents / pharmacology
Cell Size
Flecainide / pharmacology
Linear Models
Membrane Potentials / drug effects
Patch-Clamp Techniques
Potassium Channel Blockers
Potassium Channels / physiology*
Quinidine / pharmacology
Sinoatrial Node / cytology,  drug effects,  physiology*
Reg. No./Substance:
0/Anti-Arrhythmia Agents; 0/Potassium Channel Blockers; 0/Potassium Channels; 504-24-5/4-Aminopyridine; 54143-55-4/Flecainide; 56-54-2/Quinidine
Comment In:
Cardiovasc Res. 2001 Dec;52(3):517-20   [PMID:  11738069 ]

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