[Glucose stimulates the absorption of sorbitol through the human jejunal mucosa]

Digestive tolerance of sorbitol in man varies according to whether it is taken in an empty stomach or during the meal. This suggests a regulatory step in the absorption of sorbitol in the small intestine. The mechanism of intestinal transport of sorbitol was studied in vitro in jejunal fragments obtained by endoscopy or by surgery. The intracellular concentration (C) of sorbitol was measured at stationary state in the presence of 10 mmol sorbitol in the incubation medium (M). The ratio C/M was less than 1 (0.66 +/- 0.04, mean +/- SEM) and was not modified by phloridzin (0.63 +/- 0.06) or metabolic inhibitors (0.59 +/- 0.03) but was diminished by ouabain (0.5 +/- 0.05, p less than 0.05). The influx of sorbitol across the luminal membrane increased linearly with increasing concentration of sorbitol in the medium and was more pronounced in the presence of glucose (p less than 0.01). Unlike glucose, addition of sorbitol to the mucosal side did not enhance the absorption of sodium as monitored by the increase in short circuit current in Ussing chambers. A net absorption of sorbitol stimulated by glucose was observed. The absorption of sorbitol can be explained by a simple diffusional component dependent on the concentration gradient of sorbitol and by another yet unidentified mechanism stimulated by glucose.