Intestinal adaptation to protein deficiency

Feeding weanling rats a protein-deficient but energetically adequate diet leads to a marked change in intestinal architecture with no obvious change in the overall capacity to absorb amino acids ( Syme, 1982 ). Using autoradiographic localization of tritiated amino acids within enterocytes ( King et al., 1981 ), one can show that valine transport across the microvillar membrane of enterocytes is confined to the upper half of villi, whether or not these villi come from rats fed a high or low protein diet. Adaptation of the rat intestine to a protein-deficient diet occurs by a combination of reduction of villus height and mitotic rate. The net result of these changes is to preserve absorptive function at a reduced energy cost to the animal while at the same time maintaining a constant rate for enterocyte turnover.