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This Article Full Text Full Text (PDF) All Versions of this Article: 294/3/R748    most recent 00291.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Jourdan, M. Articles by Aussel, C. PubMed PubMed Citation Articles by Jourdan, M. Articles by Aussel, C.

APPETITE, OBESITY, DIGESTION, AND METABOLISM

Splanchnic sequestration of amino acids in aged rats: in vivo and ex vivo experiments using a model of isolated perfused liver

¹Laboratory of Biological Nutrition, René Descartes Paris 5 University; ²Clinical Chemistry, Hotel-Dieu Hospital Assistance Publique des Hopitaux de Paris, Paris; and ³Biology Laboratory, Emile Roux Hospital Assistance Publique des Hopitaux de Paris, Limeil-Brévannes, France

Submitted 26 April 2007 ; accepted in final form 4 December 2007

Splanchnic sequestration of amino acids (SSAA) is a process observed during aging that leads to decreased peripheral amino acid (AA) availability. The mechanisms underlying SSAA remain unknown. The aim of the present study was to determine whether a high-protein diet could increase nitrogen retention in aged rats by saturating SSAA and whether SSAA could be explained by dysregulation of hepatic nitrogen metabolism. Adult and aged male Sprague-Dawley rats were housed in individual metabolic cages and fed a normal-protein (17% protein) or high-protein diet (27%) for 2 wk. Nitrogen balance (NB) was calculated daily. On day 14, livers were isolated and perfused for 90 min to study AA and urea fluxes. NB was lower in aged rats fed a normal-protein diet than in adults, but a high-protein diet restored NB to adult levels. Isolated perfused livers from aged rats showed decreased urea production and arginine uptake, together with a release of alanine (vs. uptake in adult rats) and a hepatic accumulation of alanine. The in vivo data suggest that SSAA is a saturable process that responds to an increase in dietary protein content. The hepatic metabolism of AA in aged rats is greatly modified, and urea production decreases. This result refutes the hypothesis that SSAA is associated with an increase in AA disposal via urea production.

aging; nitrogen metabolism; isolated perfused liver; high-protein diet