Intestinal enzyme adaptation to normal diets of different composition.

Groups of rats were fed isocaloric amounts of diets rich in starch, protein, or fat. After 7 days, activities of sucrase, maltase, lactase, alkaline phosphatase, L-phenylalanylglycine hydrolase, and L-leucyl-L-alanyl hydrolase were measured in the duodenal, jejunal, and ileal mucosa of fed rats. Peptide hydrolase and alkaline phosphatase activities were significantly higher in rats fed high-protein diets, particularly in the ileum. Disaccharidases were highest in rats fed high-starch diets, especially in jejunum; the lowest activities of peptide hydrolase were seen with this diet. The high-fat diet was generally associated with intermediate activities of most enzymes, except disaccharidases, which were lowest on this diet. The different macromolecular nutrients were associated with adaptive differences in intestinal enzyme activities, which were biologically appropriate and coordinated with similar known changes in pancreatic and other enzyme activities concerned with assimilation of the particular food. However, other less interpretable changes occurred, which may have been due to effects on pancreatic secretion or on the metabolism, growth, and differentiation of intestinal cells.