DE LA HORRA PADILLA, CARMEN, Cano, M , Peral, MJ , García-Delgado, M , Durán, JM , Calonge, ML , Ilundáin, AA
Si
Biochim. Biophys. Acta-Biomembr.
Article
Científica
3.243
1.515
06/06/2001
000169415700008
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 muM D-mannose. D-Mannose uptake was inhibited by D-mannose much greater thanD-glucose > phlorizin, whereas for alpha -methyl glucopyranoside the order was D-glucose = phlorizin much greater than 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. (C) 2001 Elsevier Science B.V. All rights reserved.
intestine; kidney; brush-border membrane vesicle; sodium/D-mannose