A Na+-dependent D-mannose transporter in the apical membrane of chicken small intestine epithelial cells.
The presence of a Na+/D-mannose cotransporter in brush-border membrane vesicles (BBMV) isolated from chicken small intestine was examined. In the presence of an electrochemical gradient for Na+, but not in its absence, D-mannose was accumulated transiently by the BBMV. D-Mannose uptake into the BBMV was energized by both the membrane potential and the chemical gradient for Na+. The relationship between D-mannose transport and external D-mannose concentration was described by an equation that represented the superposition of a saturable component (Michaelis-Menten constant Km 12.5 microM) and another component unsaturatable up to 80 microM D-mannose. D-Mannose uptake was inhibited by various substances in the following order of potency: D-mannose>>D-glucose>phlorizin>phloretin>D-fructose. For the uptake of alpha-methyl-glucopyranoside the order was D-glucose=phlorizin>>phloretin=D-fructose=D-mannose. The initial rate of D-mannose uptake increased as the extravesicular [Na+] increased, with a Hill coefficient of 1, suggesting that the Na+:D-mannose cotransport stoichiometry is 1:1. It is concluded that the intestinal apical membrane has a saturable, electrogenic and concentration- and Na+-dependent mannose transport mechanism that differs from the sodium-dependent glucose transporter SGLT1.
Cano
M
M
Departamento de Fisiología y Biología Animal, Facultad de Farmacia, Universidad de Sevilla, Spain.
Calonge
M L
ML
Peral
M J
MJ
Ilundáin
A A
AA
D000818:Animals; D002250:Carbon Radioisotopes; D002645:Chickens; D004847:Epithelial Cells / Q000378:metabolism*; D005632:Fructose / Q000493:pharmacokinetics; D005947:Glucose / Q000493:pharmacokinetics; D007082:Ileum / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism; D007700:Kinetics; D008358:Mannose / Q000493:pharmacokinetics*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D008757:Methylglucosides / Q000493:pharmacokinetics; D008871:Microvilli / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D010693:Phloretin / Q000493:pharmacokinetics; D010695:Phlorhizin / Q000493:pharmacokinetics; D012964:Sodium / Q000378:metabolism*; D051269:Sodium-Glucose Transporter 1; D014316:Tritium
D002250:Carbon Radioisotopes; D008562:Membrane Glycoproteins; D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D051269:Sodium-Glucose Transporter 1; D014316:Tritium; D005632:Fructose; C027020:methylglucoside; D012964:Sodium; D010695:Phlorhizin; D005947:Glucose; D008358:Mannose; D010693:Phloretin