Mechanism of D‐Xylose Transport in Human Small Intestine

Abstract

Summary: 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 electro‐genie 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.