Document Detail


Shrinkage-induced activation of Na+/H+ exchange in rat renal mesangial cells.
MedLine Citation:
PMID:  10069995     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Using the pH-sensitive dye 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF), we examined the effect of hyperosmolar solutions, which presumably caused cell shrinkage, on intracellular pH (pHi) regulation in mesangial cells (single cells or populations) cultured from the rat kidney. The calibration of BCECF is identical in shrunken and unshrunken mesangial cells if the extracellular K+ concentration ([K+]) is adjusted to match the predicted intracellular [K+]. For pHi values between approximately 6.7 and approximately 7.4, the intrinsic buffering power in shrunken cells (600 mosmol/kgH2O) is threefold larger than in unshrunken cells (approximately 300 mosmol/kgH2O). In the nominal absence of CO2/HCO-3, exposing cell populations to a HEPES-buffered solution supplemented with approximately 300 mM mannitol (600 mosmol/kgH2O) causes steady-state pHi to increase by approximately 0.4. The pHi increase is due to activation of Na+/H+ exchange because, in single cells, it is blocked in the absence of external Na+ or in the presence of 50 microM ethylisopropylamiloride (EIPA). Preincubating cells in a Cl--free solution for at least 14 min inhibits the shrinkage-induced pHi increase by 80%. We calculated the pHi dependence of the Na+/H+ exchange rate in cell populations under normosmolar and hyperosmolar conditions by summing 1) the pHi dependence of the total acid-extrusion rate and 2) the pHi dependence of the EIPA-insensitive acid-loading rate. Shrinkage alkali shifts the pHi dependence of Na+/H+ exchange by approximately 0.7 pH units.
Authors:
M O Bevensee; E Bashi; W R Schlue; G Boyarsky; W F Boron
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  276     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1999 Mar 
Date Detail:
Created Date:  1999-04-15     Completed Date:  1999-04-15     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  C674-83     Citation Subset:  IM    
Affiliation:
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
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MeSH Terms
Descriptor/Qualifier:
Amiloride / analogs & derivatives,  pharmacology
Animals
Cells, Cultured
Chlorides / pharmacology
Fluoresceins
Fluorescent Dyes
Glomerular Mesangium / cytology,  metabolism*
Homeostasis / physiology
Hydrogen-Ion Concentration
Osmolar Concentration
Potassium / metabolism
Rats
Sodium / pharmacology
Sodium-Hydrogen Antiporter / metabolism*
Grant Support
ID/Acronym/Agency:
P01DK-17433/DK/NIDDK NIH HHS
Chemical
Reg. No./Substance:
0/Chlorides; 0/Fluoresceins; 0/Fluorescent Dyes; 0/Sodium-Hydrogen Antiporter; 1154-25-2/ethylisopropylamiloride; 2609-46-3/Amiloride; 7440-09-7/Potassium; 7440-23-5/Sodium; 85138-49-4/2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein

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


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