Postnatal Changes Of Spleen, Kidney And Lung Protein Synthesis Rates Of Fed Pigs Measured By An Intraperitoneal Flooding Dose Of L-[Ring-2h5]Phe

This study investigated the postnatal changes of spleen, kidney, and lung protein fractional synthesis rates (FSR) and their correlations with serum levels of hormones (insulin, growth hormone and cortisol), growth factors (IGF-I and GLP-2), plasma concentrations of free amino acids (AA) in fed pigs. Thirty-six purebred Yorkshire gilts were divided into suckling groups at ages of d 1, 4, 6, 12, 20 and one-week post-weaning at d 28, respectively, and received an ip injection of a flooding dose of Phe containing L-[ring-2H5]Phe (40 molar%) in saline. Serum samples before the tracer injection and plasma, spleen, lung, and kidney samples at 30 min post-injection were collected for the determinations of tracer Phe enrichments with GC-MS, plasma concentrations of free AA by HPLC, and hormones and growth factors by RIA. Tracer Phe enrichments in the plasma, spleen, kidney and lung AA free pools were flooded between 23 and 32 molar %. Postnatal FSR showed a quartic pattern of reduction in the spleen and kidney and a qintic decrease in the lung, respectively. Only serum insulin concentrations were positively correlated (P<0.05) with postnatal changes of FSR in the spleen and kidney for the hormones examined. Serum GLP-2 levels had a negative correlation (P<0.05) with postnatal changes of FSR in spleen. Plasma concentrations of free Ala, Asn, Cit, Gln, His, Leu, Lys, Met, Orn, Phe, Ser, Tau, Tyr and Val were positively correlated (P<0.05), however, Gly (P<0.05) was negatively correlated with postnatal changes of FSR in spleen, kidney or lung. These results suggest an overall curvelinear pattern of postnatal decreases of FSR in pleen, kidney and lung, which are affected by extracellular free AA concentrations as well as GLP-2 and insulin levels.