Effects of glucose, sucrose, and lactose on intestinal disaccharidases in the rat.

Abstract

Abstract Diets containing 68 per cent glucose, sucrose, or lactose were fed to 40-day-old and adult rats for 1 to 12 weeks. Whether the animals were fed ad libitum or isocalorically, small intestinal lactase, sucrase, and maltase activities were consistently and significantly greater in rats fed lactose compared to rats fed glucose, sucrose, or lab chow. The greatest differences occurred between rats fed sucrose, which had the lowest activities of all 3 disaccharidases, and those fed lactose, which had the highest. The differences were detectable after 1 week of feeding (the shortest period tested), were maximal at 3 weeks, and persisted for up to 12 weeks. They occurred in growing as well as in adult animals. When lactose was fed following sucrose, sucrase, lactase, and maltase activities increased, and when sucrose was fed following lactose, all 3 enzyme activities decreased. The higher enzyme activities associated with lactose feeding were not secondary to the starvation of animals fed lactose due to their inability to hydrolyze or absorb lactose. Dietary effects on the intestinal enzymes were greatest in the middle half of the gut. The diets did not influence gut weight or intestinal protein content; thus they affected the intestinal disaccharidase activities per se, and their influences were evident whether the enzyme activities were expressed as units per tissue protein or as units per wet weight. Neither sucrose nor lactose influenced the activity of its specific disaccharidase apart from its influence on the other disaccharidases.