Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 3 de 3
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Pflugers Arch ; 456(5): 801-12, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18214525

RESUMO

Transport activities involved in intracellular pH (pH(i)) recovery after acid or alkali challenge were investigated in cultured rat brain microvascular endothelial cells by monitoring pH(i) using a pH-sensitive dye. Following relatively small acid loads with pH(i) approximately 6.5, HCO(-)(3) influx accounted for most of the acid extrusion from the cell with both Cl(-)-independent and Cl(-)-dependent, Na(+)-dependent transporters involved. The Cl(-)-independent component has the same properties as the NBC-like transporter previously shown to account for most of the acid extrusion near the resting pH(i). Following large acid loads with pH(i) < 6.5, most of the acid extrusion was mediated by Na(+)/H(+) exchange, the rate of which was steeply dependent on pH(i). Concanamycin A, an inhibitor of V-type ATPase, had no effect on the rates of acid extrusion. Following an alkali challenge, the major component of the acid loading leading to recovery of pH(i) occurred by Cl(-)/HCO(-)(3) exchange. This exchange had the same properties as the AE-like transporter previously identified as a major acid loader near resting pH(i). These acid-loading and acid-extruding transport mechanisms together with the Na(+), K(+), ATPase may be sufficient to account not only for pH(i) regulation in brain endothelial cells but also for the net secretion of HCO(-)(3) across the blood-brain barrier.


Assuntos
Ácidos/metabolismo , Álcalis/metabolismo , Transporte Biológico/fisiologia , Encéfalo/irrigação sanguínea , Células Endoteliais/metabolismo , Concentração de Íons de Hidrogênio , Microcirculação , Ácido 4,4'-Di-Isotiocianoestilbeno-2,2'-Dissulfônico/metabolismo , Trifosfato de Adenosina/metabolismo , Amilorida/análogos & derivados , Amilorida/metabolismo , Animais , Encéfalo/citologia , Encéfalo/metabolismo , Carbonatos/metabolismo , Células Cultivadas , Cloretos/metabolismo , Desoxiglucose/metabolismo , Células Endoteliais/citologia , Fármacos Neuroprotetores/metabolismo , Ratos , Ratos Wistar , Sódio/metabolismo , ATPases Vacuolares Próton-Translocadoras/metabolismo
2.
J Physiol ; 576(Pt 3): 769-85, 2006 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-16916905

RESUMO

Fluid secretion across the blood-brain barrier, critical for maintaining the correct fluid balance in the brain, entails net secretion of HCO(3)(-), which is brought about by the combined activities of ion transporters situated in brain microvessels. These same transporters will concomitantly influence intracellular pH (pH(i)). To analyse the transporters that may be involved in the maintenance of pH(i) and hence secretion of HCO(3)(-), we have loaded primary cultured endothelial cells derived from rat brain microvessels with the pH indicator BCECF and suspended them in standard NaCl solutions buffered with Hepes or Hepes plus 5% CO(2)/HCO(3)(-). pH(i) in the standard solutions showed a slow acidification over at least 30 min, the rate being less in the presence of HCO(3)(-) than in its absence. However, after accounting for the difference in buffering, the net rates of acid loading with and without HCO(3)(-) were similar. In the nominal absence of HCO(3)(-) the rate of acid loading was increased equally by removal of external Na(+) or by inhibition of Na(+)/H(+) exchange by ethylisopropylamiloride (EIPA). By contrast, in the presence of HCO(3)(-) the increase in the rate of acid loading when Na(+) was removed was much larger and the rate was then also significantly greater than the rate observed in the absence of both Na(+) and HCO(3)(-). Removal of Cl(-) in the presence of HCO(3)(-) produced an alkalinization followed by a resumption of the slow acid gain. Removal of Na(+) following removal of Cl(-) increased the rate of acid gain. In the presence of HCO(3)(-) and initial presence of Na(+) and Cl(-), DIDS inhibited the changes in pH(i) produced by removal of either Na(+) or Cl(-). These are the expected results if these cells possess an AE-like Cl(-)/HCO(3)(-) exchanger, a 'channel-like' permeability allowing slow influx of acid (or efflux of HCO(3)(-)), a NBC-like Cl(-)-independent Na(+)-HCO(3)(-) cotransporter, and a NHE-like Na(+)/H(+) exchanger. The in vitro rates of HCO(3)(-) loading via the Na(+)-HCO(3)(-) cotransporter could, if the transporter is located on the apical, blood-facing side of the cells, account for the net secretion of HCO(3)(-) into the brain.


Assuntos
Antiportadores de Cloreto-Bicarbonato/fisiologia , Endotélio Vascular/citologia , Endotélio Vascular/fisiologia , Simportadores de Cloreto de Sódio/fisiologia , Simportadores de Sódio-Bicarbonato/fisiologia , Trocadores de Sódio-Hidrogênio/fisiologia , Ácido 4,4'-Di-Isotiocianoestilbeno-2,2'-Dissulfônico/farmacologia , Amilorida/análogos & derivados , Amilorida/farmacologia , Cloreto de Amônio/farmacologia , Animais , Barreira Hematoencefálica/fisiologia , Células Cultivadas , Endotélio Vascular/efeitos dos fármacos , Concentração de Íons de Hidrogênio , Matemática , Fármacos Neuroprotetores/farmacologia , Ratos , Ratos Wistar , ATPase Trocadora de Sódio-Potássio/fisiologia
3.
J Neurochem ; 94(5): 1420-6, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16111480

RESUMO

This study investigated mRNA expression and protein localization of equilibrative and concentrative nucleoside transporters (ENTs, CNTs) in primary cultures of rat brain endothelial cells (RBEC) and rat choroid plexus epithelial cells (RCPEC). Reverse transcriptase PCR analysis revealed that RBEC and RCPEC contained mRNA for rENT1, rENT2 and rCNT2 and for rENT1, rENT2, rCNT2 and rCNT3, respectively. Immunoblotting of membrane fractions of RBEC, fresh RCPEC and primary cultures of RCPEC revealed the presence of rENT1, rENT2 and rCNT2 proteins in all samples. Measurement of [14C]adenosine uptake into cells grown as monolayers on permeable plastic supports revealed a polarized distribution of Na+-dependent adenosine uptake in that CNT activity was associated exclusively in membranes of RBEC facing the lower chamber (which corresponds to the surface facing the interstitial fluid in situ) and in membranes of RCPEC facing the upper chamber (which corresponds to the surface facing the cerebrospinal fluid in situ). In both RBEC and RCPEC, adenosine uptake from the opposite chambers was Na+-independent and partially inhibited by nitrobenzylthioinosine, indicating the presence of the equilibrative sensitive transporter rENT1.


Assuntos
Encéfalo/irrigação sanguínea , Plexo Corióideo/metabolismo , Células Endoteliais/metabolismo , Proteínas de Transporte de Nucleosídeos/metabolismo , Adenosina/farmacocinética , Animais , Barreira Hematoencefálica , Polaridade Celular , Células Cultivadas , Plexo Corióideo/citologia , Células Epiteliais/metabolismo , Membranas Intracelulares/metabolismo , Ratos , Ratos Wistar , Sódio/farmacologia , Distribuição Tecidual
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...