Intracellular pH regulation in U-2 OS human osteosarcoma cells transfected with P-glycoprotein.
Biochim Biophys Acta
; 1542(1-3): 125-38, 2002 Jan 30.
Article
em En
| MEDLINE
| ID: mdl-11853886
ABSTRACT
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.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Osteossarcoma
/
Trocadores de Sódio-Hidrogênio
/
Membro 1 da Subfamília B de Cassetes de Ligação de ATP
Limite:
Humans
Idioma:
En
Ano de publicação:
2002
Tipo de documento:
Article