Absorption of amino acids in malnourished rats
Wapnir, R.A.; Lifshitz, F.
Journal of Nutrition 104(7): 843-849
1974
ISSN/ISBN: 0022-3166 PMID: 4209726 Document Number: 78984
The absorption of amino acids in young Wistar rats on diets low in protein or both protein and energy was studied in vivo by a perfusion technique of intestinal segments. The diets consisted of protein 18, carbohydrate 69 and fat 8% (CTL); protein 4, cellulose 14% and no change in other constituents (LPR); protein 4, carbohydrate 56.5 and cellulose 26.5% (LPC). The LPR and LPC rats failed to gain weight and became protein-deficient after eating the diets for 4 weeks. At the end of this period, the intestinal transport of tyrosine was higher in the LPR and LPC rats than in the CTL. The lumen-to-blood flow of tyrosine-3H (UL) also was increased in LPR and LPC rats; but the uptake of this amino acid by the soluble and protein-bound extracts of the intestinal mucosa was not altered and there was no relation between the absorption of tyrosine and the free amino acid values of the intestinal mucosa. The intestinal absorption of tyrosine was inversely correlated with the circulating blood tyrosine. The intestinal transport of leucine increased in malnourished animals; the whole blood concentration was unchanged. The intestinal transport rates of phenylalanine and glycine were not altered, although blood and glycine rose in both LPR and LPC rats. The absorption of lysine was lower in the LPR group while blood lysine was not modified. The results of this study suggest that in malnourished rats intestinal transport of certain neutral amino acids such as tyrosine may be inversely correlated with its concentration in the circulation.