Sodium-dependent glucose transport by cultured proximal tubule cells

The cotransport of sodium ion and α-methyl glucose, a non-metabolized hexose, was studied in rabbit proximal tubule cells cultured in defined medium. The rate of uptake of α-methyl glucose shows saturation kinetics, in which K"m, but not V"m"a"x, is dependent upon the Na^+ concentration in the med...ium. 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 α-methyl glucose also depends upon sodium concentration, consistent with the initial rate findings. The uptake of α-methyl glucose is inhibited by other sugars with the relative potencies of d-glucose > α-methyl glucose > d-galactose = 3-O methylglucose. l-Glucose, d-fructose, and d-mannose show no inhibition. Phlorizin inhibits the α-methyl glucose uptake with a K"i of 9 . 10^-^6 M. Ouabain (10^-^3 M) decreases the steady-state α-methyl glucose accumulation by 60%. In the absence of sodium, the accumulation of α-methyl glucose is 7-fold less than at 142 mM Na^+, reaching a level comparable to the sodium-independent accumulation of 3-O- Ausführliche Beschreibung Beschreibung ausblenden

1. Person:	Alavi, N.
Weitere Personen:	Spangler, R.A.; Jung, C.Y.
Quelle:	in Biochimica et Biophysica Acta (BBA)/Biomembranes Vol. 899, No. 1 (1987), p. 9-16 Weitere Artikel
Format:	Online-Artikel
Genre:	Glucose transport, Sodium dependence, Cell culture, High-affinity transport, Kinetics, Inhibition, (Rabbit proximal tubule cell)
Sprache:	English
Veröffentlicht:	1987
Beschreibung:	Online-Ressource
Online Zugang:	Online
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Anmerkung:	Copyright: Copyright (c) 2002 Elsevier Science B.V.