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Tension in skinned frog muscle fibers in solutions of varying ionic strength and neutral salt composition.
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MedLine Citation:
PMID:  4543066     Owner:  NLM     Status:  MEDLINE    
The maximal calcium-activated isometric tension produced by a skinned frog single muscle fiber falls off as the ionic strength of the solution bathing this fiber is elevated declining to zero near 0.5 M as the ionic strength is varied using KCl. When other neutral salts are used, the tension always declines at high ionic strength, but there is some difference between the various neutral salts used. The anions and cations can be ordered in terms of their ability to inhibit the maximal calcium-activated tension. The order of increasing inhibition of tension (decreasing tension) at high ionic strength for anions is propionate(-) approximately SO(4) (--) < Cl(-) < Br(-). The order of increasing inhibition of calcium-activated tension for cations is K(+) approximately Na(+) approximately TMA(+) < TEA(+) < TPrA(+) < TBuA(+). The decline of maximal calcium-activated isometric tension with elevated salt concentration (ionic strength) can quantitatively explain the decline of isometric tetanic tension of a frog muscle fiber bathed in a hypertonic solution if one assumes that the internal ionic strength of a muscle fiber in normal Ringer's solution is 0.14-0.17 M. There is an increase in the base-line tension of a skinned muscle fiber bathed in a relaxing solution (no added calcium and 3 mM EGTA) of low ionic strength. This tension, which has no correlate in the intact fiber in hypotonic solutions, appears to be a noncalcium-activated tension and correlates more with a declining ionic strength than with small changes in [MgATP], [Mg], pH buffer, or [EGTA]. It is dependent upon the specific neutral salts used with cations being ordered in increasing inhibition of this noncalcium-activated tension (decreasing tension) as TPrA(+) < TMA(+) < K(+) approximately Na(+). Measurements of potentials inside these skinned muscle fibers bathed in relaxing solutions produced occasional small positive values (<6 mV) which were not significantly different from zero.
A M Gordon; R E Godt; S K Donaldson; C E Harris
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  The Journal of general physiology     Volume:  62     ISSN:  0022-1295     ISO Abbreviation:  J. Gen. Physiol.     Publication Date:  1973 Nov 
Date Detail:
Created Date:  1974-01-14     Completed Date:  1974-01-14     Revised Date:  2010-09-13    
Medline Journal Info:
Nlm Unique ID:  2985110R     Medline TA:  J Gen Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  550-74     Citation Subset:  IM    
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MeSH Terms
Bromides / pharmacology
Calcium / pharmacology
Chlorides / pharmacology
Hypertonic Solutions
Magnesium / pharmacology
Muscle Contraction*
Muscles / physiology*
Potassium Chloride / pharmacology
Rana pipiens
Sodium / pharmacology
Sulfates / pharmacology
Reg. No./Substance:
0/Bromides; 0/Chlorides; 0/Hypertonic Solutions; 0/Ions; 0/Sulfates; 7439-95-4/Magnesium; 7440-23-5/Sodium; 7440-70-2/Calcium; 7447-40-7/Potassium Chloride

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

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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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Copyright © 1973 by The Rockefeller University Press
Received Day: 30 Month: 3 Year: 1973
Print publication date: Day: 1 Month: 11 Year: 1973
Volume: 62 Issue: 5
First Page: 550 Last Page: 574
ID: 2226133
PubMed Id: 4543066

Tension in Skinned Frog Muscle Fibers in Solutions of Varying Ionic Strength and Neutral Salt Composition
A. M. Gordon
R. E. Godt
S. K. B. Donaldson
C. E. Harris
From the Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195.
Dr. Harris's present address is the Department of Biochemistry, University of Washington School of Medicine, Seattle, Washington 98195

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