Document Detail

Role of individual ionic current systems in the SA node hypothesized by a model study.
MedLine Citation:
PMID:  12877768     Owner:  NLM     Status:  MEDLINE    
This paper discusses the development of a cardiac sinoatrial (SA) node pacemaker model. The model successfully reconstructs the experimental action potentials at various concentrations of external Ca2+ and K+. Increasing the amplitude of L-type Ca2+ current (I(CaL)) prolongs the duration of the action potential and thereby slightly decreases the spontaneous rate. On the other hand, a negative voltage shift of I(CaL) gating by a few mV markedly increases the spontaneous rate. When the amplitude of sustained inward current (I(st)) is increased, the spontaneous rate is increased irrespective of the I(CaL) amplitude. Increasing [Ca2+](o) shortens the action potential and increases the spontaneous rate. When the spontaneous activity is stopped by decreasing I(CaL) amplitude, the resting potential is nearly constant (-35 mV) over 1-15 mM [K+](o) as observed in the experiment. This is because the conductance of the inward background non-selective cation current balances with the outward [K+](o)-dependent K+ conductance. The unique role of individual voltage- and time-dependent ion channels is clearly demonstrated and distinguished from that of the background current by calculating an instantaneous zero current potential ("lead potential") during the course of the spontaneous activity.
Nobuaki Sarai; Satoshi Matsuoka; Shinobu Kuratomi; Kyoichi Ono; Akinori Noma
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Japanese journal of physiology     Volume:  53     ISSN:  0021-521X     ISO Abbreviation:  Jpn. J. Physiol.     Publication Date:  2003 Apr 
Date Detail:
Created Date:  2003-07-24     Completed Date:  2004-05-11     Revised Date:  2007-03-21    
Medline Journal Info:
Nlm Unique ID:  2985184R     Medline TA:  Jpn J Physiol     Country:  Japan    
Other Details:
Languages:  eng     Pagination:  125-34     Citation Subset:  IM    
Department of Physiology and Biophysics, Kyoto University Graduate School of Medicine, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
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MeSH Terms
Action Potentials / physiology
Biological Clocks / physiology
Calcium / metabolism*
Calcium Channels / physiology
Calcium Channels, L-Type / physiology
Computer Simulation
Diastole / physiology
Guinea Pigs
Ion Channels / physiology*
Ion Transport / physiology
Ions / analysis,  metabolism
Membrane Potentials / physiology
Models, Biological*
Myocytes, Cardiac / physiology
Potassium / metabolism
Sinoatrial Node / cytology,  physiology*
Reg. No./Substance:
0/Calcium Channels; 0/Calcium Channels, L-Type; 0/Ion Channels; 0/Ions; 7440-09-7/Potassium; 7440-70-2/Calcium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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