Amino Acid Supplementation Does Not Alter Whole-Body Phenylalanine Kinetics in Arabian Geldings

作者：Urschel Kristine L^*; Geor Raymond J; Hanigan Mark D; Harris Pat A

来源：Journal of Nutrition, 2012, 142(3): 461-469.

DOI：10.3945/jn.111.149906

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-C-13] 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 mu mol/kg), constant (6 mu mol.kg(-1).h(-1)) i.v. infusion of L-[1-C-13] 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 = 51, 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 %26lt; 0.05). Isotopic plateau was attained in blood [1-C-13] phenylalanine and breath (CO2)-C-13 enrichments by 60 and 270 min, respectively. Phenylalanine flux (+20%) and oxidation (+110%) were greater (P %26lt; 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. J. Nutr. 142: 461-469, 2012.

• 出版日期2012-3
• 单位Virginia Tech; 美国弗吉尼亚理工大学(Virginia Tech)