Intestinal maturation in the rat: the role of enteral nutrients.

In order to investigate the role of enteral nutrients in intestinal maturation, an animal model was developed consisting of provision of intravenous nutrient infusions to immature suckling rats over the period of weaning. Age- and litter-matched controls were provided identical amounts of the parenteral solution by entered cannula using the same model. At the end of the period of weaning, animals were killed and the intestines removed for measurement of morphologic parameters and disaccharidase, DNA, and protein levels. The absence of enteral nutrients during weaning resulted in striking inhibition of intestinal growth, diminution in mucosal cell mass, and delayed development of lactase. Although the appearance of sucrase was not affected by the lack of enteral nutrients, sucrase levels rose to only one-third of control levels. Jejunoileal gradients were not present in animals deprived of enteral nutrients but were present in animals receiving enteral nutrients. These results are distinct from adult animals treated in identical experimental fashion and indicate that major parameters of intestinal maturation are altered by the absence of intraluminal nutrients. A critical role for intraluminal nutrients in regulation of intestinal development is therefore suggested. The animal model developed for these studies is well suited for investigation of the interactions of the intraluminal environment with intestinal maturation.