Document Detail

Delayed rectification in the calf cardiac Purkinje fiber. Evidence for multiple state kinetics.
MedLine Citation:
PMID:  2413917     Owner:  NLM     Status:  MEDLINE    
We have investigated the delayed rectifier current (Ix) in the calf cardiac Purkinje fiber using a conventional two-microelectrode voltage clamp arrangement. The deactivation of Ix was monitored by studying decaying current tails after the application of depolarizing voltage prepulses. The reversal potential (Vrev) of these Ix tails was measured as a function of prepulse magnitude and duration to test for possible permeant ion accumulation- or depletion-induced changes in Vrev. We found that prepulse-induced changes in Vrev were less than 5 mV, provided that prepulse durations were less than or equal to 3.5 s and magnitudes were less than or equal to +35 mV. We kept voltage pulse structures within these limits for the remainder of the experiments in this study. We studied the sensitivity of Vrev to variation in extracellular K+. The reversal potential for Ix is well described by a Goldman-Hodgkin-Katz relation for a channel permeable to Na+ and K+ with PNa/PK = 0.02. The deactivation of Ix was always found to be biexponential and the two components shared a common reversal potential. These results suggest that it is not necessary to postulate the existence of two populations of channels to account for the time course of the Ix tails. Rather, our results can quantitatively be reproduced by a model in which the Ix channel can exist in three (two closed, one open) conformational states connected by voltage dependent rate constants.
P B Bennett; L C McKinney; R S Kass; T Begenisich
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biophysical journal     Volume:  48     ISSN:  0006-3495     ISO Abbreviation:  Biophys. J.     Publication Date:  1985 Oct 
Date Detail:
Created Date:  1985-12-18     Completed Date:  1985-12-18     Revised Date:  2010-09-09    
Medline Journal Info:
Nlm Unique ID:  0370626     Medline TA:  Biophys J     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  553-67     Citation Subset:  IM    
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MeSH Terms
Calcium / pharmacology
Electric Conductivity
Extracellular Space / physiology
Heart Conduction System / physiology*
Ion Channels / drug effects,  physiology
Membrane Potentials / drug effects
Nifedipine / analogs & derivatives,  pharmacology
Potassium / metabolism
Purkinje Fibers / drug effects,  physiology*
Vasodilator Agents / pharmacology
Reg. No./Substance:
0/Ion Channels; 0/Vasodilator Agents; 21829-25-4/Nifedipine; 63675-72-9/Nisoldipine; 7440-09-7/Potassium; 7440-70-2/Calcium

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