Co-expression of an anion conductance pathway with Na(+)-glucose cotransport in rat renal brush-border membrane vesicles.
Brush-border membrane vesicles were prepared from superficial rat renal cortex by a Mg(2+)-precipitation technique. The initial (20 s) [14C]glucose uptake rate from solutions containing 100 mmol/l Na (salt) was found to be dependent upon the anion composition of the medium; in comparison to gluconate-containing medium (0.46 +/- 0.05 nmol/mg protein), Cl- accelerated the initial rate to 1.47 +/- 0.21 nmol/mg protein (n = 4 preparations, +/- SEM). This enhancement was reduced by 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 0.5 mmol/l), but was unaffected by 4,4'-diisothiocyanatostilbene 2,2'-disulphonate (DIDS, 0.5 mmol/l). When membrane vesicles were pre-equilibrated with 100 mmol/l K (salt) and 100 mmol/l mannitol and glucose uptake was measured from a solution containing 100 mmol/l Na gluconate and 100 mmol/l mannitol in the presence of 80 mumol/l valinomycin (to generate an outward K+ diffusion electrical p. d.), it was found that intravesicular KCl depressed the initial glucose uptake compared to K gluconate. NPPB (0.5 mmol/l) increased the initial glucose uptake with intravesicular KCl towards values seen in K gluconate vesicles. In conditions where the only driving force for glucose uptake was established by an inward anion gradient (Nao = Nai) it was found that inward Cl- gradients could drive uphill glucose transport and that this was sensitive to NPPB (0.5 mmol/l), but insensitive to DIDS. We conclude that a Cl- conductance co-exists with Na-cotransport in rat renal brush-border membrane vesicles prepared from superficial renal cortex and this may function to regulate the activity of electrogenic transport systems at this membrane.
Brown
C D
CD
Department of Physiological Sciences, Medical School, The University, Newcastle upon Tyne.
King
N
N
Simmons
N L
NL
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002712:Chlorides / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D009579:Nitrobenzoates / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism*
D002712:Chlorides; D007473:Ion Channels; D009579:Nitrobenzoates; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D011189:Potassium Chloride; D012964:Sodium; D005947:Glucose; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid