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Effects of ionic strength on the regulation of Na/H exchange and K-Cl cotransport in dog red blood cells.
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MedLine Citation:
PMID:  7561739     Owner:  NLM     Status:  MEDLINE    
Dog red cell membranes contain two distinct volume-sensitive transporters: swelling-activated K-Cl cotransport and shrinkage-activated Na/H exchange. Cells were prepared with intracellular salt concentration and weight percentage of cell water (%cw) varied independently by transient permeabilization of the cell membrane to cations. The dependence of transporter-mediated Na and K influxes upon %cw and upon extracellular salt concentration (c(ext)) was measured in cells so prepared. It was found that the critical value of %cw at which transporters are activated, called the set point, is similar for the two transporters, and that the set points for the two transporters decrease similarly with increasing extracellular salt concentration. These findings suggest a common mechanism of regulation of these two transporters. Cellular Na, K, and Cl concentrations were measured as functions of %cw and c(ext). Using these data together with data from the literature for other solute concentrations, empirical expressions were developed to describe the dependence of the intracellular concentrations of all significant small molecule electrolytes, and therefore the intracellular ionic strength, upon %cw and c(ext). A mechanistic model for the dependence of the set point of an individual transporter upon intracellular ionic strength is proposed. According to this model, the set point represents a critical extent of association between the transporter and a postulated soluble regulatory protein, called regulator. Model functions are presented for the calculation of the thermodynamic activity of regulator, and hence extent of regulator-transporter association, as a function of total intracellular protein concentration (or %cw) and ionic strength. The experimentally observed dependence of set point %cw on c(ext) are simulated using these functions and the empirical expressions described above, together with reasonable but not uniquely determined values of model parameters.
J C Parker; P B Dunham; A P Minton
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of general physiology     Volume:  105     ISSN:  0022-1295     ISO Abbreviation:  J. Gen. Physiol.     Publication Date:  1995 Jun 
Date Detail:
Created Date:  1995-11-14     Completed Date:  1995-11-14     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:  677-99     Citation Subset:  IM    
Department of Medicine, University of North Carolina, Chapel Hill 27599, USA.
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MeSH Terms
Body Water / metabolism
Carrier Proteins / blood*
Chlorides / blood
Erythrocyte Membrane / metabolism
Erythrocytes / metabolism*
Hemoglobins / metabolism
Models, Biological
Osmolar Concentration
Potassium / blood
Sodium / blood
Sodium-Hydrogen Antiporter / blood*
Grant Support
Reg. No./Substance:
0/Carrier Proteins; 0/Chlorides; 0/Hemoglobins; 0/Sodium-Hydrogen Antiporter; 0/Symporters; 0/potassium-chloride symporters; 7440-09-7/Potassium; 7440-23-5/Sodium

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: 6 Year: 1995
Volume: 105 Issue: 6
First Page: 677 Last Page: 699
ID: 2216953
Publisher Id: 96047263
PubMed Id: 7561739

Effects of ionic strength on the regulation of Na/H exchange and K-Cl cotransport in dog red blood cells

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