Monosaccharide absorption and water secretion during disaccharide perfusion of the human jejunum

During jejunal perfusion of normal subjects with isotonic mannitol-saline containing glucose, maltose or sucrose (112 mmol/l), monosaccharide absorption from disaccharides was greater than expected from the intraluminal concentration of free monosaccharides, and water secretion was greater than with glucose. With equimolar (112 mmol/l) glucose + disaccharide mixtures, intraluminal glucose concentrations were similar to but total glucose absorption less than expected from experiments with the individual sugars. The results favour sequential hydrolysis-absorption whereby high concentrations of monosaccharide accumulate at the brush border and promote sugar uptake by conventional rather than 'disaccharidase-related' transport, and stimulate water secretion by local osmotic effects.