title: Somatotropin increases protein balance by lowering body protein degradation in fed, growing pigs.
abstract: Somatotropin (ST) administration enhances protein deposition in well-nourished, growing animals. To determine whether the anabolic effect is due to an increase in protein synthesis or a decrease in proteolysis, pair-fed, weight-matched ( approximately 20 kg) growing swine were treated with porcine ST (150 microg. kg(-1). day(-1), n = 6) or diluent (n = 6) for 7 days. Whole body leucine appearance (R(a)), nonoxidative leucine disposal (NOLD), urea production, and leucine oxidation, as well as tissue protein synthesis (K(s)), were determined in the fed steady state using primed continuous infusions of [(13)C]leucine, [(13)C]bicarbonate, and [(15)N(2)]urea. ST treatment increased the efficiency with which the diet was used for growth. ST treatment also increased plasma insulin-like growth factor I (+100%) and insulin (+125%) concentrations and decreased plasma urea nitrogen concentrations (-53%). ST-treated pigs had lower leucine R(a) (-33%), leucine oxidation (-63%), and urea production (-70%). However, ST treatment altered neither NOLD nor K(s) in the longissimus dorsi, semitendinosus, or gastrocnemius muscles, liver, or jejunum. The results suggest that in the fed state, ST treatment of growing swine increases protein deposition primarily through a suppression of protein degradation and amino acid catabolism rather than a stimulation of protein synthesis.
authors.affiliation: United States Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Vann
authors.forename: H V
authors.initials: HV
authors.lastname: Nguyen
authors.forename: P J
authors.initials: PJ
authors.lastname: Reeds
authors.forename: D G
authors.initials: DG
authors.lastname: Burrin
authors.forename: M L
authors.initials: ML
authors.lastname: Fiorotto
authors.forename: N C
authors.initials: NC
authors.lastname: Steele
authors.forename: D R
authors.initials: DR
authors.lastname: Deaver
authors.forename: T A
authors.initials: TA
authors.lastname: Davis
mesh_terms: D000818:Animals; D001806:Blood Urea Nitrogen; D001835:Body Weight / Q000187:drug effects; D004435:Eating / Q000502:physiology*; D013006:Growth Hormone / Q000494:pharmacology*; D006728:Hormones / Q000097:blood; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007930:Leucine / Q000378:metabolism; D008297:Male; D010084:Oxidation-Reduction; D011506:Proteins / Q000378:metabolism*; D013552:Swine / Q000254:growth & development; D014508:Urea / Q000378:metabolism
chemical_list: D006728:Hormones; D007328:Insulin; D011506:Proteins; D007334:Insulin-Like Growth Factor I; D014508:Urea; D013006:Growth Hormone; D007930:Leucine