Mechanism of D-xylose transport in human small intestine.
The transport mechanism of D-xylose across the mucosal border of small intestine was investigated in humans both in vitro and in vivo. A comparative study was also made between infants and adults. We investigated the Na+ dependence of D-xylose influx from the mucosal solution into the epithelial cells, the phlorizin sensitivity of the influx, transport kinetics and electrogenic property of the D-xylose transport. The results of kinetic study indicated that the transport of D-xylose was completely diffusional. The influx of D-xylose across the mucosal border of human small intestine was Na+ independent and phlorizin insensitive. The electrical property of D-xylose transport could not be observed. There was no difference in the characteristics of D-xylose transport between small intestines of infants or adults. These results in the present study suggest that D-xylose does not share a common transport mechanism of D-glucose, and xylose tolerance test does not give any information about the absorptive capacity of D-glucose.
D000328:Adult; D000368:Aged; D001692:Biological Transport / Q000187:drug effects; D002675:Child, Preschool; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007223:Infant; D007583:Jejunum / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010695:Phlorhizin / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
D012964:Sodium; D014994:Xylose; D010695:Phlorhizin; D005947:Glucose