Sodium-dependent glucose transport by cultured proximal tubule cells.
Biochim Biophys Acta
; 899(1): 9-16, 1987 May 12.
Article
em En
| MEDLINE
| ID: mdl-3567195
ABSTRACT
The cotransport of sodium ion and alpha-methyl glucose, a non-metabolized hexose, was studied in rabbit proximal tubule cells cultured in defined medium. The rate of uptake of alpha-methyl glucose shows saturation kinetics, in which Km, but not Vmax, is dependent upon the Na+ concentration in the medium. The transport system was found to be of the high-affinity type, characteristic of the straight portion of the proximal tubule. Analysis of the rates of initial uptake within the context of a generalized cotransport model, suggests that two Na+ ions are bound in the activation of the hexose transport. The steady-state level of accumulation of alpha-methyl glucose also depends upon sodium concentration, consistent with the initial rate findings. The uptake of alpha-methyl glucose is inhibited by other sugars with the relative potencies of D-glucose greater than alpha-methyl glucose greater than D-galactose = 3-O methylglucose. L-Glucose, D-fructose, and D-mannose show no inhibition. Phlorizin inhibits the alpha-methyl glucose uptake with a Ki of 9 X 10(-6) M. Ouabain (10(-3) M) decreases the steady-state alpha-methyl glucose accumulation by 60%. In the absence of sodium, the accumulation of alpha-methyl glucose is 7-fold less than at 142 mM Na+, reaching a level comparable to the sodium-independent accumulation of 3-O-methyl-D-glucose. These findings are similar to those observed in the proximal tubule of the intact kidney.
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Base de dados:
MEDLINE
Assunto principal:
Sódio
/
Túbulos Renais Proximais
/
Metilglucosídeos
/
Metilglicosídeos
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
1987
Tipo de documento:
Article