Route of administration (enteral or parenteral) affects the contribution of L-glutamine to de novo L-arginine synthesis in mice: a stable-isotope study |
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Authors: | Boelens Petra G Melis Gerdien C van Leeuwen Paul A ten Have Gabrie A Deutz Nicolaas E |
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Institution: | Department of Surgery, Vrije Universiteit. Medical Center, PO Box 7057, 1007 MB Amsterdam, The Netherlands. |
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Abstract: | A pathway from enteral L-glutamine as substrate for L-arginine synthesis is suggested by previous studies. L-Glutamine and L-glutamine dipeptides exhibit numerous beneficial effects in experimental and clinical studies. In trauma patients, enteral L-glutamine supply increased plasma L-arginine. The present study was designed to quantify the contribution of L-glutamine to the de novo L-citrulline and L-arginine synthesis in mice when L-glutamine is administered in a high dose of labeled L-glutamine or L-alanyl-L-glutamine by the enteral or parenteral route. For this purpose, male Swiss mice (n = 43) underwent a laparotomy, and catheters were inserted for sampling and infusion. A primed, constant, and continuous infusion of L-alanyl-L-2-(15)N]glutamine (dipeptide groups) or L-2-(15)N]glutamine (free L-glutamine groups), simultaneously with L-ureido-(13)C,(2)H(2)]citrulline and L-guanidino-(15)N(2),(2)H(2)]arginine, was given (steady-state model). Mice received the L-glutamine tracers intravenously (jugular vein) or enterally (duodenum). Enrichments of metabolites were measured by LC-MS. Arterial L-glutamine concentrations were the highest in the intravenous dipeptide group. L-Glutamine was converted to L-citrulline and L-arginine when L-2-(15)N]glutamine and L-alanyl-L-2-(15)N]glutamine were given by enteral or parenteral route. The contribution of L-glutamine to the de novo synthesis of L-citrulline and L-arginine was higher in the enteral groups when compared with the intravenous groups (P < 0.005). Therefore, the route of administration (enteral or parenteral) affects the contribution of L-glutamine, provided as free molecule or dipeptide, to the de novo synthesis of L-arginine in mice. |
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