Document Detail

Intracellular pH regulation in U-2 OS human osteosarcoma cells transfected with P-glycoprotein.
MedLine Citation:
PMID:  11853886     Owner:  NLM     Status:  MEDLINE    
The molecular mechanisms responsible for intracellular pH regulation in the U2-OS osteosarcoma cell line were investigated by loading with 2',7'-bis(2-carboxyethyl)-5(6) carboxyfluorescein ester and manipulation of Cl(-) and Na(+) gradients, both in HEPES- and HCO(3)(-)/CO(2)-buffered media. Both acidification and alkalinisation were poorly sensitive to 4,4'-diisothiocyanate dihydrostilbene-2,2'-disulfonic acid, inhibitor of the anion exchanger, but sensitive to amiloride, inhibitor of the Na(+)/H(+) exchanger. In addition to the amiloride-sensitive Na(+)/H(+) exchanger, another H(+) extruding mechanism was detected in U-2 OS cells, the Na(+)-dependent HCO(3)(-)/Cl(-) exchanger. No significant difference in resting pH(i) and in the rate of acidification or alkalinisation was observed in clones obtained from U-2 OS cells by transfection with the MDR1 gene and overexpressing P-glycoprotein. However, both V(max) and K' values for intracellular [H(+)] of the Na(+)/H(+) exchanger were significantly reduced in MDR1-transfected clones, in the absence and/or presence of drug selection, in comparison to vector-transfected or parental cell line. NHE1, NHE5 and at a lower extent NHE2 mRNA were detected in similar amount in all U2-OS clones. It is concluded that, although overexpression of P-glycoprotein did not impair pH(i) regulation in U-2 OS cells, the kinetic parameters of the Na(+)/H(+) exchanger were altered, suggesting a functional relationship between the two membrane proteins.
Anna Maria Porcelli; Katia Scotlandi; Rosaria Strammiello; Gabriella Gislimberti; Nicola Baldini; Michela Rugolo
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1542     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  2002 Jan 
Date Detail:
Created Date:  2002-03-07     Completed Date:  2002-04-23     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  125-38     Citation Subset:  IM    
Dipartimento di Biologia Evoluzionistica Sperimentale, Università di Bologna, Italy.
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MeSH Terms
Chloride-Bicarbonate Antiporters / metabolism
Hydrogen-Ion Concentration
Osteosarcoma / chemistry*,  genetics,  metabolism
P-Glycoprotein / biosynthesis*,  genetics
Protein Isoforms / metabolism
Sodium Bicarbonate
Sodium Chloride
Sodium-Hydrogen Antiporter / metabolism*
Tumor Cells, Cultured
Reg. No./Substance:
0/Buffers; 0/Chloride-Bicarbonate Antiporters; 0/Fluoresceins; 0/P-Glycoprotein; 0/Protein Isoforms; 0/Sodium-Hydrogen Antiporter; 144-55-8/Sodium Bicarbonate; 2609-46-3/Amiloride; 7647-14-5/Sodium Chloride; 85138-49-4/2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein

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