QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Liechty, E. A. Articles by Denne, S. C. Search for Related Content PubMed PubMed Citation Articles by Liechty, E. A. Articles by Denne, S. C.

---

Nutrient Metabolism

Aromatic Amino Acids Are Utilized and Protein Synthesis Is Stimulated during Amino Acid Infusion in the Ovine Fetus¹

Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202

²To whom correspondence should be addressed.

The purpose of this study was to determine whether the ovine fetus is capable of increased disposal of an amino acid load; if so, would it respond by increased protein synthesis, amino acid catabolism or both? A further purpose of the study was to determine whether the pathways of aromatic amino acid catabolism are functional in the fetus. Late gestation ovine fetuses of well-nourished ewes received an infusion of Aminosyn PF alone (APF), and Aminosyn PF + glycyl-L-tyrosine (APF+GT) at rates estimated to double the intake of these amino acids. The initial study, using APF, was performed at 126 ± 1.4 d; the APF+GT study was performed at 132 ± 1.7 d (term = 150 d). Phenylalanine and tyrosine kinetics were determined using both stable and radioactive isotopes. Plasma concentrations of most amino acids, but not tyrosine, increased during both studies; tyrosine concentration increased only during the APF+GT study. Phenylalanine rate of appearance and phenylalanine hydroxylation increased during both studies. Tyrosine rate of appearance increased only during the APF+GT study; tyrosine oxidation did not increase during either study. Fetal protein synthesis increased significantly during both studies, producing a significant increase in fetal protein accretion. Fetal proteolysis was unchanged in response to either amino acid infusion. These results indicate that the fetus responds to an acute increase in amino acid supply primarily by increasing protein synthesis and accretion, with a smaller but significant increase in amino acid catabolism also. Both phenylalanine hydroxylation and tyrosine oxidation are active in the fetus, and the fetus is able to increase phenylalanine hydroxylation rapidly in response to increased supply.

KEY WORDS: • phenylalanine hydroxylation • stable isotopes • amino acid metabolism • mass spectrometry • sheep

This article has been cited by other articles:

				L. D. Brown, P. J. Rozance, J. S. Barry, J. E. Friedman, and W. W. Hay Jr. Insulin is required for amino acid stimulation of dual pathways for translational control in skeletal muscle in the late-gestation ovine fetus Am J Physiol Endocrinol Metab, January 1, 2009; 296(1): E56 - E63. [Abstract] [Full Text] [PDF]

				J. N. MacLachlan, S. Hemstreet, B. Matushewski, J. D. McCallum, and B. S. Richardson Induced Hyper and Hypo Amino Acidemia in the Ovine Fetus Near Term: Effects on Electrocortical Activity Reproductive Sciences, September 1, 2008; 15(7): 710 - 719. [Abstract] [PDF]

				C. H. P. van den Akker, F. W. J. te Braake, W. W. Rovekamp-Abels, and J. B. van Goudoever Quality of Amino Acid Solutions for Preterm Infants Pediatrics, April 1, 2008; 121(4): 865 - 866. [Full Text] [PDF]

				H A de Boo and J E Harding Protein metabolism in preterm infants with particular reference to intrauterine growth restriction Arch. Dis. Child. Fetal Neonatal Ed., July 1, 2007; 92(4): F315 - F319. [Abstract] [Full Text] [PDF]

				J. E. H. Bunt, T. Rietveld, H. Schierbeek, J. L. D. Wattimena, L. J. I. Zimmermann, and J. B. van Goudoever Albumin synthesis in preterm infants on the first day of life studied with [1-13C]leucine Am J Physiol Gastrointest Liver Physiol, April 1, 2007; 292(4): G1157 - G1161. [Abstract] [Full Text] [PDF]

				L. D. Brown and W. W. Hay Jr. Effect of hyperinsulinemia on amino acid utilization and oxidation independent of glucose metabolism in the ovine fetus Am J Physiol Endocrinol Metab, December 1, 2006; 291(6): E1333 - E1340. [Abstract] [Full Text] [PDF]

				W. Shen, P. Wisniowski, S. C. Denne, D. W. Boyle, and E. A. Liechty Anabolic effects of insulin and IGF-I in the ovine fetus are reduced by prolonged maternal fasting Am J Physiol Endocrinol Metab, May 1, 2005; 288(5): E907 - E913. [Abstract] [Full Text] [PDF]

				W. Shen, P. Wisniowski, L. Ahmed, D. W. Boyle, S. C. Denne, and E. A. Liechty Protein anabolic effects of insulin and IGF-I in the ovine fetus Am J Physiol Endocrinol Metab, April 1, 2003; 284(4): E748 - E756. [Abstract] [Full Text] [PDF]