Whole-body synthesis of l-homoarginine in pigs and rats supplemented with l-arginine
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Recent studies suggest an important role for l-homoarginine in cardiovascular, hepatic and neurological functions, as well as the regulation of glucose metabolism. However, little is known about whole-body l-homoarginine synthesis or its response to dietary l-arginine intake in animals. Four series of experiments were conducted to determine l-homoarginine synthesis and catabolism in pigs and rats. In Experiment 1, male and female pigs were fed a corn- and soybean meal-based diet supplemented with 0.0–2.42 % l-arginine-HCl. In Experiment 2, male and female rats were fed a casein-based diet, while receiving drinking water containing supplemental l-arginine-HCl to provide 0.0-3.6 g l-arginine/kg body-weight/day. In both experiments, urine collected from the animals for 24 h was analyzed for l-homoarginine and related metabolites. In Experiment 3, pigs and rats received a single oral dose of 1 or 10 mg l-homoarginine/kg body-weight, respectively, and their urine was collected for 24 h for analyses of l-homoarginine and related substances. In Experiment 4, slices of pig and rat tissues (including liver, brain, kidney, heart, and skeletal-muscle) were incubated for 1 h in Krebs-bicarbonate buffer containing 5 or 50 µM l-homoarginine. Our results indicated that: (a) animal tissues did not degrade L-homoarginine in the presence of physiological concentrations of other amino-acids; (b) 95–96 % of orally administered l-homoarginine was recovered in urine; (c) l-homoarginine was quantitatively a minor product of l-arginineg catabolism in the body; and (d) dietary l-arginine supplementation dose-dependently increased whole-body l-homoarginine synthesis. These novel findings provide a new framework for future studies of l-homoarginine metabolism and physiology in animals and humans.
KeywordsArginine Homoarginine Animals Metabolism Synthesis
High-performance liquid chromatography
Nitrite plus nitrate
This research was supported by grants from Hubei Provincial Key Project for Scientific and Technical Innovation (2014ABA022), Hubei Hundred Talent program, Natural Science Foundation of Hubei Province (2013CFA097 and 2013CFB325), the International Council of Amino Acid Science (Brussels, Belgium), the Agriculture and Food Research Initiative Competitive Grant from the Animal Growth & Nutrient Utilization Program of the USDA National Institute of Food and Agriculture (2014-67015-21770), and Texas A&M AgriLife Research (H-8200). Y.Q. Hou, D.S. Che, and F.L. Wang were supported by Fellowships from the China Scholarship Council.
Compliance with ethical standards
The use of animals for this research was approved by the Institutional Animal Care and Use Committee of Texas A&M University.
Conflict of interest
The authors declare that they have no conflict of interest.
This was an animal study and did not involve informed consent.
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