Document Detail

Influence of changes in external potassium and chloride ions on membrane potential and intracellular potassium ion activity in rabbit ventricular muscle.
MedLine Citation:
PMID:  1271296     Owner:  NLM     Status:  MEDLINE    
1. The membrane responses of rabbit papillary muscles to rapid changes in [K](o) and [Cl](o) were measured with open-tipped micropipettes and with closed micropipettes made from K-selective glass.2. The muscle cells behaved primarily as a K electrode, and responses to changes in [K](o) with constant [Cl](o) or with constant [K](o) x [Cl](o) were substantially the same.3. When [Cl](o) was changed at a constant [K](o) the membrane potentials changed rapidly and symmetrically by a small value and remained constant for 30 min.4. Measurement of potential with K(+)-selective micro-electrodes in these experiments showed no change in intracellular K activity. In addition to permitting calculation of K permeability, these measurements reassured us that the K(+)-selective electrodes were well insulated and not influenced by electrical shunts at the impalement site.5. Although the membrane response to changes in [Cl](o) was small, it was possible to calculate that the permeability ratio (P(Cl)/P(K)), was 0.11. The Cl and K conductances were about 0.015 mmho/cm(2) and 0.09 mmho/cm(2) respectively, resulting in a conductance ratio (g(Cl)/g(K)) of about 0.17.6. The time course of depolarization by increase in [K](o) was rapid (half-time 5 sec), but repolarization on return to lower [K](o) was much slower (half-time 50 sec). The depolarization time course was easily fitted by the potential change calculated by assuming the need for K diffusion into the extracellular spaces and taking account of the logarithmic relation between membrane potential and [K](o). These calculations did not fit the time course of repolarization, which was slowed in the fashion expected from an inward-rectifying membrane.7. The influence of [K](i) on membrane potential was investigated by changes in tonicity of the external solution. Hypotonic solution produced a change in intracellular K activity close to that produced by ideal water movement. However, in hypertonic solution, intracellular K activity did not rise as much as predicted, suggesting a change in intracellular activity coefficient.
H A Fozzard; C O Lee
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Journal of physiology     Volume:  256     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1976 Apr 
Date Detail:
Created Date:  1976-08-02     Completed Date:  1976-08-02     Revised Date:  2010-09-07    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  663-89     Citation Subset:  IM    
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MeSH Terms
Chlorides / pharmacology*
Electric Conductivity
Intracellular Fluid / analysis
Membrane Potentials / drug effects*
Muscles / metabolism*
Papillary Muscles / metabolism
Potassium / analysis,  metabolism,  pharmacology*
Reg. No./Substance:
0/Chlorides; 7440-09-7/Potassium

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

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