[Glucose absorption from mono- and oligosaccharide solutions in the rat small intestine in vivo]

The rates of maltose and maltotriose hydrolysis, and glucose absorption in the isolated loop of the rat small intestine, perfused by isocaloric solutions of the above substrates, were examined in chronic experiments. In all the experiments, the rates of glucose absorption from the solutions of maltose and maltotriose (M- and MT-glucose, respectively) were almost the same as those from the isocaloric solutions of free glucose (G-glucose). The rate of water absorption in the isolated intestinal loop was significantly higher under the perfusion with maltose (100 mM) and maltotriose (66.6 mM) solutions than under the perfusion with equivalent glucose solutions. The results of mathematical simulation, in which absorptive surface of the small intestine was approximated as a folded surface with an adjoining zone of diffusion, were in a good agreement with the experimental data. The model showed that in the range of physiological concentrations of the substrates their transfer across the pre-epithelial layer by water flux seemed to play a minor role as compared with a transfer by diffusion. According the results obtained, the most significant factors that influence the efficiency of coupling between hydrolysis and absorption of nutrients, are following: a complex geometry of intestinal surface, the pre-epithelial diffusion layer, the rate of water absorption (secretion) in the intestine.