Comparative in vivo and in vitro effect of mono- and disaccharides on intestinal brush border enzyme activities in suckling rats.

Suckling rats were bottle fed during 48 h with a basic diet enriched with different mono- or disaccharides. In parallel, explants of intestinal mucosa were cultured in vitro for 48 h in the presence or in the absence of a synthetic glucocorticoid (dexamethasone) and with or without different carbohydrates. In both studies, enzyme activities were assayed on purified brush border membranes. From these combined in vivo and in vitro investigations it appeared that (1) there is a highly specific stimulation of mono- and disaccharides on the corresponding brush border disaccharidases: glucose, fructose, sucrose on sucrase and maltase activities, fructose being generally the most potent activator. Other brush border enzymes were not modified by the dietary carbohydrates. (2) These sugar-mediated effects were obtained only in the presence of glucocorticoids. This hormone alone induced the appearance of a slight sucrase activity and provoked a stimulation of maltase activity. The results show clearly that glucocorticoids are necessary to induce sucrase activity, but that the level of this activity is under the strict dependence of the dietary carbohydrates.