Postprandial Changes in the Function of Digestive Organs in Rats Meal-fed Twice a Day with 40% Casein-based and Protein-free Diets

Abstract

Growing rats were meal-fed twice a day in the morning (9:00-11:00) and night (20:0-22:00) with 40% casein-based and protein-free diets in turn, or vice versa. Twenty-five days later, the animals were killed by fours in each group at 9:00, 11:00, 14:00, and 18:00, to excise their small intestines and pancreas. Immediately the jejunal mucosa was scraped together and assayed for [³H]leucine incorporation into protein as well as [³H]leucine absorption in epithelial cells. Concurrently with the assay, tissue-specific hydrolase activities were measured. Although small intestinal intrinsic hydrolases did not fluctuate much in activity, the activities of digestive enzymes in the pancreas increased after the intake of the 40% casein-based diet and decreased after the intake of the protein-free diet. This can be accounted for by the supply of synthesis materials for these digestive enzymes. Interestingly a reverse tendency was observed for both the in vitro 'protein synthesis' and 'amino acid transport' capacities of jejunal mucosal scrapings. Such functional changes are probably under the control of circadian rhythm cued by a feeding schedule.