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The mechanism of rectification of iK1 in canine Purkinje myocytes.
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MedLine Citation:
PMID:  1698915     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We have characterized the inward rectifying background potassium current, iK1, of canine cardiac Purkinje myocytes in terms of its reversal potential, voltage activation curve, and "steady-state" current-voltage relation. The latter parameter was defined from the difference current between holding currents in the presence and absence of 20 mM cesium. Our data suggest that iK1 rectification does not arise exclusively from voltage-dependent gating or exclusively from voltage-dependent blockade by internal magnesium ions. The voltage activation curve constructed from tail currents fit to a Boltzmann two-state model predicts less outward current than is actually observed. The magnesium-dependent rectification due to channel blockade is too fast to account for the time-dependent gating of iK1 that gives rise to the tail currents. We propose a new model of rectification that assumes that magnesium blockade of the channel occurs simultaneously with voltage-dependent gating. The new model incorporates the kinetic schema elaborated by Matsuda, H. (1988. J. Physiol. 397:237-258) to explain the appearance of subconducting states of the iK1 channel in the presence of blocking ions. That schema suggested that iK1 channels were composed of three parallel pores, each of which could be blocked independently. In our model we considered the consequences of partial blockade of the channel. If the channels are partially blocked at potentials where normally they are mostly gated closed, and if the partially blocked channels cannot close, then blockade will have the paradoxical result of enhancing the current carried by iK1.
Authors:
C Oliva; I S Cohen; P Pennefather
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of general physiology     Volume:  96     ISSN:  0022-1295     ISO Abbreviation:  J. Gen. Physiol.     Publication Date:  1990 Aug 
Date Detail:
Created Date:  1990-11-15     Completed Date:  1990-11-15     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2985110R     Medline TA:  J Gen Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  299-318     Citation Subset:  IM    
Affiliation:
Department of Physiology and Biophysics, H.S.C., State University of New York, Stony Brook 11794.
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MeSH Terms
Descriptor/Qualifier:
Adenosine Triphosphate / pharmacology
Animals
Cesium / pharmacology
Dogs
Dose-Response Relationship, Drug
Electric Conductivity / drug effects,  physiology*
Ion Channels / drug effects,  physiology,  ultrastructure
Magnesium / pharmacology
Membrane Potentials / drug effects,  physiology*
Models, Biological
Purkinje Fibers / cytology*,  physiology,  ultrastructure
Grant Support
ID/Acronym/Agency:
HL-20558/HL/NHLBI NIH HHS; HL-28958/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
0/Ion Channels; 56-65-5/Adenosine Triphosphate; 7439-95-4/Magnesium; 7440-46-2/Cesium
Comments/Corrections

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

Full Text
Journal Information
Journal ID (nlm-ta): J Gen Physiol
ISSN: 0022-1295
ISSN: 1540-7748
Publisher: The Rockefeller University Press
Article Information
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Print publication date: Day: 1 Month: 8 Year: 1990
Volume: 96 Issue: 2
First Page: 299 Last Page: 318
ID: 2228993
Publisher Id: 91011326
PubMed Id: 1698915

The mechanism of rectification of iK1 in canine Purkinje myocytes


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