In vitro oxidation of essential amino acids by jejunal mucosal cells of growing pigs

This study was conducted to test the hypothesis that porcine jejunal mucosal cells can degrade all essential amino acids (EAA). Jejunal mucosal cells (primarily enterocytes) were isolated from 50-day-old healthy pigs and incubated at 37 °C for 45 min in Krebs buffer containing plasma concentrations of amino acids and one of the following l-[1-14C]- or l-[U-14C]-amino acids plus unlabeled tracers at 0.5, 2, or 5 mM: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. There was active transamination of leucine, isoleucine and valine in the cells (1.35–2.5 nmol/mg protein per 45 min at 2 mM), with most (67–71%) of their α-ketoacids released into the medium. In contrast, catabolism of methionine and phenylalanine was negligible (0.04–0.05 nmol/mg protein per 45 min at 2 mM) and that of other EAA was completely absent in these cells. These results indicate that intestinal mucosal cells are a site for the substantial degradation of branched-chain amino acids but not other EAA in pigs.