Rates and Mechanisms of Glucose, Galactose, and Xylose Absorption in Man in Vivo

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Abstract
Jejunal absorption-rates of glucose, galactose, and xylose were determined consecutively, using a double-lumen tube perfusion technique, in 6 Arab subjects in vivo; perfusion solutions contained 200 mmol/l of each monosaccharide. Mean xylose absorption rate was significantly lower than that for glucose (P < 0.001) and galactose (P < 0.001). In order to investigate evidence that glucose and xylose share the same jejunal transfer mechanism, their absorption-rates when given alone and together, at high concentrations, were determined in 6 other Arabs; perfusion solutions contained (1) 200 mmol/l glucose, (2) 100 mmol/l xylose, and (3) 200 mmol/l glucose + 100 mmol/l xylose. Rates of glucose and xylose absorption were not significantly influenced by the other monosaccharide. This study does not therefore confirm existence of a common transfer mechanism. A significant correlation between absorption rate of glucose and weight of xylose excreted after a 25 g oral load (P < 0.05) was demonstrated.