INFLUENCE OF PROTEIN-INTAKE ON WHOLE-BODY AND SPLANCHNIC LEUCINE KINETICS IN HUMANS

The influence of the protein content of the meal on protein turnover w as investigated in the splanchnic bed and in the remaining parts of th e body in humans. Two groups of five subjects consumed every 20 min a liquid formula providing either 1.5 g protein.kg(-1).day(-1) (P) or no protein (PF). L-[1-C-13]leucine and L-[5,5,5-H-2(3)] leucine were adm inistered by vein and gut, respectively. An open two-pool model was de veloped to calculate leucine kinetics in both compartments, with the a ssumption that the enrichment of the tracers incorporated into very lo w density lipoprotein apolipoprotein B100 at isotopic steady state cou ld reflect the leucine labeling in the splanchnic region. Nonsplanchni c uptake and release of leucine were not significantly different in th e two groups. Within the splanchnic area, leucine uptake was 2.1 times higher in the P than in the PF group (P < 0.01), whereas leucine rele ase was reduced but not significantly (-19%) in the P group compared w ith the PF group. Moreover, data derived from this model showed that p rotein intake induced an increase in whole body protein synthesis and no change in whole body protein breakdown. Albumin synthesis, as well as its contribution to whole body protein synthesis, was significantly enhanced by protein intake.