Fractional protein synthesis rates measured by an intraperitoneal injection of a flooding dose of L-[ring-2H5]phenylalanine in pigs.
Our objectives were to examine the effect of an i.p. injection of a flooding dose of l-phenylalanine (Phe) containing l-[ring-(2)H(5)]Phe on time courses of physiologic responses, the tracer Phe enrichments, and fractional protein synthesis rates (FSR) in plasma, visceral organs, and muscles. In a randomized complete block design, 5 blocks of 5 littermate piglets were weaned at 16 d of age and injected i.p. with a flooding dose of l-Phe (1.5 mmol/kg body weight) on d 8 postweaning under fed conditions. Tissues were collected at 15, 30, 45, 60, and 75 min postinjection. Plasma glucose concentration increased (cubic effect, P < 0.05) from 4.8 preinjection to 5.8 mmol/L 15 min postinjection and returned to preinjection levels thereafter. Plasma insulin concentration did not change (P > 0.05) over time. Plasma Phe concentration increased logarithmically (P < 0.05) from 85 to 711 micromol/L and reached 95% of the maximum concentration 48 min postinjection, but no changes (P > 0.05) in tissue contents of other free amino acids were observed. The Phe free pools in plasma, visceral organs, and muscles were evenly enriched (32.3 +/- 1.4 mol%) with l-[(2)H(5)]Phe 15 min after the i.p. injection. The FSR in visceral organs did not change (P > 0.05), whereas plasma and muscle protein FSR decreased (P < 0.05) over time. We conclude that the i.p. injected tracer Phe rapidly distributed into plasma and intra- and extracellular spaces, and was effective for measuring FSR in visceral organs, but not in plasma and muscles of pigs.
Bregendahl
Kristjan
K
Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada. kristjan@iastate.edu
Liu
Lijuan
L
Cant
John P
JP
Bayley
Henry S
HS
McBride
Brian W
BW
Milligan
Larry P
LP
Yen
Jong-Tseng
JT
Fan
Ming Z
MZ
D000596:Amino Acids / Q000097:blood*; D000818:Animals; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D007274:Injections, Intraperitoneal; D010649:Phenylalanine / Q000008:administration & dosage / Q000494:pharmacology* / Q000502:physiology; D014176:Protein Biosynthesis; D013552:Swine; D014018:Tissue Distribution
D000596:Amino Acids; D010649:Phenylalanine