The intrinsic Cl- conductance of mouse kidney cortex brush-border membrane vesicles is not related to CFTR.
Brush-border membrane vesicles (BBMV) were prepared from whole Balb/c mice kidneys by a Mg2+ precipitation technique. The presence of an intrinsic Cl- conductance co-expressed with Na+/glucose cotransport was inferred by the anion dependence of [14C]glucose uptake and overshoot with inward Na(+)-anion gradients. In Na(+)-equilibrated conditions, an inside-negative membrane potential difference (p.d.) produced by an inward Cl- gradient alone was capable of driving intravesicular [14C]glucose accumulation. The apparent anion conductance had a selectivity of Br- = I- = Cl- > F- > > gluconate, was inhibited by 0.5 mM 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) but was unaffected by 0.5 mM 4,4'-diisothiocyanatostilbene 2,2'-disulphonate (DIDS). BBMV were isolated from mice in which the CFTR gene had been disrupted by a termination mutation (-/-) and compared with normal litter mates (+/+) and heterozygotes (-/+)[18]. [14C]Glucose uptake in NaCl media was significantly greater than glucose uptake in Na gluconate media for all three genotypes measured at 20 s: for homozygous -/- animals [14C]glucose uptake was increased by 2.80 +/- 0.53 fold in Cl- media compared to gluconate media, n = 6; for wild-type +/+, by 2.16 +/- 0.53 fold, n = 8; and for heterozygous +/- animals, by 2.17 +/- 0.45 fold, n = 8. The observation of a Cl-(-)dependent component in BBMV isolated from homozygous -/- mutant animals shows that the chloride conductance in these vesicles cannot be due to CFTR expression.
King
N
N
Department of Physiological Sciences, University of Newcastle upon Tyne, Medical School, UK.
Colledge
W H
WH
Ratcliff
R
R
Evans
M J
MJ
Simmons
N L
NL
D000818:Animals; D018118:Chloride Channels / Q000502:physiology; D002712:Chlorides / Q000378:metabolism / Q000502:physiology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology*; D004553:Electric Conductivity; D007672:Kidney Cortex / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008871:Microvilli / Q000502:physiology; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1
D018118:Chloride Channels; D002712:Chlorides; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D051269:Sodium-Glucose Transporter 1; D019005:Cystic Fibrosis Transmembrane Conductance Regulator