Contribution of the digestive tract and the liver to the whole body metabolism of phenylalanine and leucine in growing lambs

摘要

The aim of the present study was to measure the contribution of the liver and the portal drained viscera (PDV) to the metabolic fluxes of amino acids (AA) in ruminants when animals were submitted to a diet deficient in nitrogen (N). A better understanding of the regulation of AA and N utilisation at the splanchnic level can give important tools to improve the efficiency of production of muscle or milk proteins. However, previous work (Lobley et al., 1996) has shown that even if most studies are usingone single AA as a tracer (and make extrapolations to whole body kinetics), the differences in the utilisation of the AA by the various tissues and organs and metabolic routes can lead to misleading estimates. Consequently, the present study used two AAas tracers: leucine (Leu) and phenylalanine (Phe) to assess the metabolic fluxes of the whole body and through the PDV, liver and the splanchnic tissues. These two tracers were chosen because of their different metabolic fates (and intensity of utilisation) in the splanchnic and the peripheral tissues (Reynolds, 2006).