Na/Ca exchange in the basolateral membrane of the A6 cell monolayer: role in Cai homeostasis.
Pflugers Arch
; 430(1): 105-14, 1995 May.
Article
en En
| MEDLINE
| ID: mdl-7667070
The presence of a Na/Ca exchanger in A6 cells was investigated by measuring intracellular calcium (Cai) fluctuations and the 45Ca fluxes through the basolateral membranes (blm) of the cell monolayer. Removal of Na+ from the medium produced a transient increase in Cai followed by a regulatory phase returning Cai to control levels in 3-4 min, this phase being greatly accelerated (< 60 s) by NaCl addition (apparent Km of approximately 5 mM Na+). The Cai increase was only found with the Na(+)-free medium on the basolateral side of the cell monolayer. A twofold increase in the 45Ca influx was observed under these conditions. In Ca(2+)- depleted cells, the initial Cai increase after Ca2+ addition to the medium was greater when the putative Na/Ca exchanger was not functioning (i.e. in a Na(+)-free medium). 45Ca effluxes through the blm of the monolayer were greatly and transiently increased by a Na(+)-free medium on the serosal side and blocked by orthovanadate (1 mM). The Cai increased induced by a hypo-osmotic shock was greater in cells bathed in a Na(+)-medium, conditions expected to block the activity of the Na/Ca exchanger. These findings support the hypothesis that a Na/Ca exchanger is present on the blm of A6 cells and affirm its role in Cai homeostasis in steady-state conditions and following osmotic shock. In addition, a Ca2+ pump also located on the blm and Ca2+ stores sensitive to inositol 1,4,5-trisphosphate were found to be implicated in Cai homeostasis.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Sodio
/
Proteínas Portadoras
/
Membrana Celular
/
Calcio
Límite:
Animals
Idioma:
En
Revista:
Pflugers Arch
Año:
1995
Tipo del documento:
Article
País de afiliación:
Francia
Pais de publicación:
Alemania