Na(+)-dependent D-mannose transport at the apical membrane of rat small intestine and kidney cortex.
The presence of a Na(+)/D-mannose cotransport activity in brush-border membrane vesicles (BBMV), isolated from either rat small intestine or rat kidney cortex, is examined. In the presence of an electrochemical Na(+) gradient, but not in its absence, D-mannose was transiently accumulated by the BBMV. D-Mannose uptake into the BBMV was energized by both the electrical membrane potential and the Na(+) chemical gradient. D-Mannose transport vs. external D-mannose concentration can be described by an equation that represents a superposition of a saturable component and another component that cannot be saturated up to 50 microM D-mannose. D-Mannose uptake was inhibited by D-mannose >> D-glucose>phlorizin, whereas for alpha-methyl glucopyranoside the order was D-glucose=phlorizin >> D-mannose. The initial rate of D-mannose uptake increased as the extravesicular Na(+) concentration increased, with a Hill coefficient of 1, suggesting that the Na(+):D-mannose cotransport stoichiometry is 1:1. It is concluded that both rat intestinal and renal apical membrane have a concentrative, saturable, electrogenic and Na(+)-dependent D-mannose transport mechanism, which is different from SGLT1.
De la Horra
M C
MC
Departamento de Fisiología y Biología Animal, Facultad de Farmacia, Universidad de Sevilla, C) Tramontana s/n, 41012, Sevilla, Spain.
Cano
M
M
Peral
M J
MJ
García-Delgado
M
M
Durán
J M
JM
Calonge
M L
ML
Ilundáin
A A
AA
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D007413:Intestinal Mucosa / Q000502:physiology*; D007421:Intestine, Small / Q000502:physiology*; D007583:Jejunum / Q000502:physiology; D007672:Kidney Cortex / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008358:Mannose / Q000378:metabolism*; D008564:Membrane Potentials; D008757:Methylglucosides / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism / Q000502:physiology*; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism*
D008757:Methylglucosides; C027020:methylglucoside; D012964:Sodium; D008358:Mannose