TY - JOUR
T1 - Amino acid supplementation does not alter whole-body phenylalanine kinetics in Arabian geldings
AU - Urschel, Kristine L.
AU - Geor, Raymond J.
AU - Hanigan, Mark D.
AU - Harris, Pat A.
PY - 2012/3/1
Y1 - 2012/3/1
N2 - Stable isotope infusion methods have not been extensively used in horses to study protein metabolism. The objectives were to develop infusion and sampling methodologies for [1-13C] phenylalanine and apply these methods to determine whether the addition of supplemental amino acids to a control diet affected whole-body phenylalanine kinetics in mature horses. Arabian geldings were studied using a 6-h primed (9 μmol/kg), constant (6 μmol kg-1 h-1) i.v. infusion of L-[1-13C] phenylalanine, with blood and breath sampled every 30 min, to measure whole-body phenylalanine kinetics in response to receiving the control diet (n = 12) or the control diet supplemented with equimolar amounts of glutamate (+Glu; 55 mg kg-1 d-1; n = 5), leucine (+Leu; 49 mg kg-1 d-1; n = 5), lysine (+Lys; 55 mg kg-1 d-1; n = 5), or phenylalanine (+Phe; 62 mg kg-1 d-1; n = 6). The plasma concentrations of the supplemented amino acid in horses receiving the +Leu, +Lys, and +Phe diets were 58, 53, and 36% greater, respectively, than for the control treatment (P < 0.05). Isotopic plateau was attained in blood [1-13C] phenylalanine and breath 13CO2 enrichments by 60 and 270 min, respectively. Phenylalanine flux (+20%) and oxidation (+110%) were greater (P < 0.05) in horses receiving the +Phe treatment than in those fed the control diet. There was no effect of treatment diet on nonoxidative phenylalanine disposal or phenylalanine release from protein breakdown. The developed methods are a valuable way to study protein metabolism and assess dietary amino acid adequacy in horses and will provide a useful tool for studying amino acid requirements in the future.
AB - Stable isotope infusion methods have not been extensively used in horses to study protein metabolism. The objectives were to develop infusion and sampling methodologies for [1-13C] phenylalanine and apply these methods to determine whether the addition of supplemental amino acids to a control diet affected whole-body phenylalanine kinetics in mature horses. Arabian geldings were studied using a 6-h primed (9 μmol/kg), constant (6 μmol kg-1 h-1) i.v. infusion of L-[1-13C] phenylalanine, with blood and breath sampled every 30 min, to measure whole-body phenylalanine kinetics in response to receiving the control diet (n = 12) or the control diet supplemented with equimolar amounts of glutamate (+Glu; 55 mg kg-1 d-1; n = 5), leucine (+Leu; 49 mg kg-1 d-1; n = 5), lysine (+Lys; 55 mg kg-1 d-1; n = 5), or phenylalanine (+Phe; 62 mg kg-1 d-1; n = 6). The plasma concentrations of the supplemented amino acid in horses receiving the +Leu, +Lys, and +Phe diets were 58, 53, and 36% greater, respectively, than for the control treatment (P < 0.05). Isotopic plateau was attained in blood [1-13C] phenylalanine and breath 13CO2 enrichments by 60 and 270 min, respectively. Phenylalanine flux (+20%) and oxidation (+110%) were greater (P < 0.05) in horses receiving the +Phe treatment than in those fed the control diet. There was no effect of treatment diet on nonoxidative phenylalanine disposal or phenylalanine release from protein breakdown. The developed methods are a valuable way to study protein metabolism and assess dietary amino acid adequacy in horses and will provide a useful tool for studying amino acid requirements in the future.
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U2 - 10.3945/jn.111.149906
DO - 10.3945/jn.111.149906
M3 - Article
C2 - 22259192
AN - SCOPUS:84858163219
VL - 142
SP - 461
EP - 469
IS - 3
ER -