Glycobiology Advance Access originally published online on March 19, 2004
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Glycobiology vol 14 no 6 pp. 495-500, 2004
Glycobiology vol. 14 no. 6 © Oxford University Press 2004; all rights reserved.
D-mannose transport and metabolism in isolated enterocytes
Dept. Fisiología y Biología Animal, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain
Received on June 3, 2003; revised on October 1, 2003; accepted on January 11, 2004
D-mannose transport and metabolism has been studied in enterocytes isolated from chicken small intestine. In the presence of Na+, the mannose taken up by the cells either remains free, is phosphorylated, is catabolized to H2O, or becomes part of membrane components. The mannose remaining free in the cytosol is released when the cells are transferred to an ice bath. The Na+-dependent D-mannose transport is electrogenic and inhibited by ouabain and dinitrophenol; its substrate specificity differs from SGLT-1 transporter. The Glut2 transporter inhibitors phloretin and cytochalasin B added following 30-min mannose uptake reduced the previously accumulated D-mannose, whereas these two agents increased the cell to external medium 3-O-methyl-glucose (3-OMG) concentration ratio. D-mannose efflux rate from preloaded D-[2-3H]-mannose enterocytes is Na+-independent. Phloretin did not affect D-mannose efflux rate, whereas it inhibited that of 3-OMG. Neither mannose uptake nor efflux rate were affected by fructose. It is concluded that part of the mannose taken up by the enterocytes is rapidly metabolized and that enterocytes have two D- mannose transport systems: one is concentrative and Na+-dependent and the other is Na+-independent and passive.
1 To whom correspondence should be addressed; e-mail: ilundain{at}us.es
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