THE UPTAKE OF GLUTAMINE AND RELEASE OF ARGININE, CITRULLINE AND PROLINE BY THE SMALL-INTESTINE OF DEVELOPING PIGS

Arteriovenous (A-V) plasma concentrations of amino jejunum were studie d in preweaning (14- to 21-d-old) and post-weaning (29- to 58-d-old) p igs in the postabsorptive state. Glutamine was the only amino acid tha t was extracted by the small intestine in both pre- and post-weaning p igs. The production of citrulline by the jejunum was low in preweaning pigs, but was threefold greater in the post-weaning pigs than in the preweaning pigs. The output of proline by the intestine was observed i n the post-weaning pigs but not in the preweaning pigs. Arginine and a lanine were the predominant amino acids released by the jejunum of the pre- and post-weaning pigs, respectively. Whereas glutamate was the m ajor amino acid formed from glutamine in pig enterocytes in vitro, the Jejunum of the post-weaning pigs released comparable amounts of citru lline, proline and glutamate in vivo. There were no significant A-V di fferences in the concentrations of urea, ornithine, taurine, tyrosine, serine, glycine and nutritionally essential amino acids in either the preweaning or the post-weaning pigs. Thus, we demonstrated for the fi rst time the uptake in vivo of glutamine and the release of arginine, alanine, citrulline, glutamate and proline by the small intestine of d eveloping pigs. Our findings on the release in vivo of citrulline (the precursor of arginine) and proline by the small intestine of the pre- and post-weaning pigs provide a basis for explaining why arginine and proline are nutritionally essential amino acids for young suckling pi glets but not for adult pigs.