Effect of aging on intestinal absorption of aromatic amino acids in vitro in the rat.
Whole-thickness everted jejunal rings were used to measure uptake of L-tyrosine (L-Tyr), L-phenylalanine (L-Phe), and L-tryptophan (L-Trp) in 6-, 12-, and 24-mo-old rats. The rate of uptake of all three amino acids (1 mM) was significantly reduced after 20 min of incubation in 24-mo-old compared with 6-mo-old rats. Results of influx (2 min) of 0.5-40.0 mM L-Phe and L-Trp suggested an increased affinity but decreased capacity for the transporter with age; these differences were significant for L-Trp (P less than 0.05). Respective values for apparent Kt and Vmax were the following: L-Phe 6-mo-old rats, 5.46 mM and 1.03 mumol.g-1.2 min-1; 24-mo-old rats, 2.54 mM and 0.51 mumol.g-1.2 min-1; L-Trp 6-mo-old rats, 5.09 mM and 0.38 mumol.g-1.2 min-1; 24-mo-old rats, 3.20 mM and 0.25 mumol.g-1.2 min-1. Values for 12-mo-old rats fell in between the other two age groups.
Navab
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F
Department of Medicine, University of Arkansas for Medical Sciences, Little Rock 72205.
Winter
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CG
D000375:Aging; D000818:Animals; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007583:Jejunum / Q000254:growth & development* / Q000378:metabolism; D007700:Kinetics; D008297:Male; D010649:Phenylalanine / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D014364:Tryptophan / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan