Xylose transport pathways in rabbit ileum.
The D-xylose transepithelial transport mechanism was examined in rabbit ileum in vitro. The net flux of D-xylose (Jxylnet) from mucosa to serosa is abolished in the presence of 10(-4) M ouabain. D-Xylose stimulates the net flux of sodium (JNanet) and the short-circuit current (Isc) equally. The D-xylose concentration at which delta Isc reaches half its maximal value is 70 +/- 5 mM. The steady-state intracellular D-xylose concentration ([X]c) is lower than the extracellular concentration in all the situations examined. However, [X]c is Na dependent. The unidirectional influx across the luminal membrane (Jxyl m leads to c) decreases by 50% in the absence of Na; the Na-dependent Jxyl m leads to c is entirely inhibited by D-galactose (40 mM). However, in the absence of Na, Jxyl m leads to c is not inhibited by D-galactose, D-fructose, D-mannose, 2-deoxy-D-glucose  or phloretin. In the absence of Na, J xyl m leads to c is a linear function of extracellular D-xylose concentrations up to 300 mM. In the presence of 10 mM D-glucose, there is a linear relationship between transepithelial D-xylose permeability, and polyethylene glycol (4,000 mol wt) permeability. These results indicate the possible existence of a cellular and a paracellular route for D-xylose and related molecules.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D003847:Deoxyglucose / Q000494:pharmacology; D005690:Galactose / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D007082:Ileum / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D010693:Phloretin / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D014994:Xylose / Q000378:metabolism* / Q000494:pharmacology
D003847:Deoxyglucose; D012964:Sodium; D014994:Xylose; D005947:Glucose; D010693:Phloretin; D005690:Galactose