Document Detail


pH regulation in single glomerular mesangial cells. I. Acid extrusion in absence and presence of HCO3-.
MedLine Citation:
PMID:  2849306     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We have developed a technique to measure the fluorescence of a pH-sensitive dye (2,7-biscarboxyethyl-5(6)-carboxyfluorescein) in single glomerular mesangial cells in culture. The intracellular fluorescence excitation ratio of the dye was calibrated using the nigericin-high-K+ approach. In the absence of CO2-HCO3-, mesangial cells that are acid loaded by an NH+4 prepulse exhibit a spontaneous intracellular pH (pHi) recovery that is blocked either by ethylisopropylamiloride (EIPA) or removal of external Na+. This pHi recovery most probably reflects the activity of a Na+-H+ exchanger. When the cells are switched from a N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered solution to one containing CO2-HCO3-, there is an abrupt acidification due to CO2 entry, which is followed by a spontaneous recovery of pHi to a steady-state value higher than that prevailing in HEPES. Both the rate of recovery and the higher steady-state pHi imply that the application of CO2-HCO3- introduces an increase in net acid extrusion from the cell. One third of total net acid extrusion in CO2-HCO3- is EIPA sensitive and most likely is mediated by the Na+-H+ exchanger. The remaining two thirds of acid extrusion could be caused by a decrease in the background acid-loading rate and/or the introduction of a new, HCO3- -dependent acid-extrusion mechanism. The HCO3- -induced alkalinization cannot be accounted for by a HCO3- -induced reduction in the acid-loading rate. The latter can be estimated by applying EIPA in the absence of HCO3- and observing the rate of pHi decline. We found that this acid-loading rate is only about one fifth as great as the total net acid extrusion rate in the presence of HCO3-. Indeed, two thirds of net acid extrusion in HCO3- is blocked by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), an inhibitor of HCO3- -dependent transport. Furthermore, the effects of EIPA and SITS were additive. Thus, in the presence of CO2-HCO3-, a SITS-sensitive-HCO3- -dependent transporter is the dominant mechanism of acid extrusion. This mechanism also accounts for the increase in steady-state pHi on addition of CO2-HCO3-.
Authors:
G Boyarsky; M B Ganz; R B Sterzel; W F Boron
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  255     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1988 Dec 
Date Detail:
Created Date:  1989-01-26     Completed Date:  1989-01-26     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:  C844-56     Citation Subset:  IM    
Affiliation:
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
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MeSH Terms
Descriptor/Qualifier:
4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / pharmacology
Amiloride / analogs & derivatives,  pharmacology
Ammonia / pharmacology
Animals
Bicarbonates / pharmacology*
Cells, Cultured
Glomerular Mesangium / drug effects,  metabolism*
Hydrogen-Ion Concentration*
Kinetics
Rats
Spectrometry, Fluorescence / instrumentation,  methods
Grant Support
ID/Acronym/Agency:
GM-07527/GM/NIGMS NIH HHS; K01 DK01022/DK/NIDDK NIH HHS
Chemical
Reg. No./Substance:
0/Bicarbonates; 1154-25-2/ethylisopropylamiloride; 2609-46-3/Amiloride; 27816-59-7/4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 7664-41-7/Ammonia

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


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