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.
Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada. kristjan@iastate.edu
Kristjan
K
Bregendahl
Lijuan
L
Liu
John P
JP
Cant
Henry S
HS
Bayley
Brian W
BW
McBride
Larry P
LP
Milligan
Jong-Tseng
JT
Yen
Ming Z
MZ
Fan
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