Document Detail


Factors affecting ammonium uptake by C11 clone of MDCK cells.
MedLine Citation:
PMID:  12457240     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
In several tissues ammonium ions are able to use the transport pathways of other ions, particularly of K+. We investigated this possibility in the C11 clone of MDCK cells, thought to represent intercalated cells, in control and 0 Cl- conditions. Cell pH was measured by ratiometric fluorescence microscopy using the pH indicator BCECF. After preincubating the cells for 10 min in control or 0 Cl- (substituted by gluconate) Ringer, an ammonium pulse was applied to induce cell acidification. The magnitude of the initial alkalinization (DeltapH) was 0.24+/-0.03 ( n=28) pH units in controls, which fell to 0.023+/-0.01 ( n=12) in 0 Cl-, suggesting uptake of NH4+ balancing the alkalinization by NH3. Addition of 10(-3) M bumetanide or furosemide to the 0 Cl- medium, or 10(-4 )M hexamethylene amiloride, did not alter DeltapH. However, with 5 mM Ba+, DeltapH increased to 38% of control. When 2.5x10(-4) M ouabain, an inhibitor of Na+-K+ ATPase, was used, DeltapH increased to 46% of control. Inhibition of H+-K+ ATPase by SCH28080 or by omeprazol caused significant increase in DeltapH. In 0 Cl- solution, these cells underwent a mean volume reduction (-d V) of -10.24+/-1.96% per 10 min as measured by confocal microscopy. To investigate if NH4+ influx was regulated by cell volume or by cell Cl-, volume reduction was avoided by two procedures. When preincubating with NPPB, a Cl- channel blocker, in 0 Cl-, volume reduction was inhibited (d V=-2.12% per 10 min), and DeltapH was 0.24+/-0.04 ( n=5). When the cells were preincubated in hypotonic 0 Cl- (260 mosmol/l), cell volume reduction was abolished (d V=+2.6% per 10 min) and DeltapH was 0.52+/-0.07 ( n=7). Thus, activation of NH4+ influx by several transporters was due to volume reduction rather than to [Cl-] alteration.
Authors:
A L Tararthuch; R Fernandez; M A Ramirez; G Malnic
Publication Detail:
Type:  Journal Article     Date:  2002-09-11
Journal Detail:
Title:  Pflügers Archiv : European journal of physiology     Volume:  445     ISSN:  0031-6768     ISO Abbreviation:  Pflugers Arch.     Publication Date:  2002 Nov 
Date Detail:
Created Date:  2002-11-28     Completed Date:  2003-07-29     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0154720     Medline TA:  Pflugers Arch     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  194-201     Citation Subset:  IM    
Affiliation:
Depto. Fisiologia e Biofísica, Instituto de Ciências Biomédicas, University of São Paulo, Av. Prof. Lineu Prestes 1524, 05508-900 São Paulo, Brasil.
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MeSH Terms
Descriptor/Qualifier:
Animals
Barium / pharmacology
Calcium Channel Blockers / pharmacology
Cell Line
Cell Size
Chlorides
Clone Cells
Dogs
Enzyme Inhibitors / pharmacology
H(+)-K(+)-Exchanging ATPase / antagonists & inhibitors,  metabolism
Hydrogen-Ion Concentration
Hypotonic Solutions / pharmacology
Imidazoles / pharmacology
Isotonic Solutions / chemistry,  pharmacology
Nephrons / cytology,  drug effects,  metabolism*
Nitrobenzoates / pharmacology
Omeprazole / pharmacology
Ouabain / pharmacology
Quaternary Ammonium Compounds / pharmacokinetics*
Sodium-Potassium-Exchanging ATPase / antagonists & inhibitors,  metabolism
Chemical
Reg. No./Substance:
0/Calcium Channel Blockers; 0/Chlorides; 0/Enzyme Inhibitors; 0/Hypotonic Solutions; 0/Imidazoles; 0/Isotonic Solutions; 0/Nitrobenzoates; 0/Quaternary Ammonium Compounds; 107254-86-4/5-nitro-2-(3-phenylpropylamino)benzoic acid; 630-60-4/Ouabain; 73590-58-6/Omeprazole; 7440-39-3/Barium; 76081-98-6/Sch 28080; 8026-10-6/Ringer's solution; EC 3.6.1.10/H(+)-K(+)-Exchanging ATPase; EC 3.6.3.9/Sodium-Potassium-Exchanging ATPase

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