Substrate oxidation by the portal drained viscera of fed piglets

Fully fed piglets (28 days old, 7-8 kg) bearing portal, arterial, and gastr ic catheters and a portal flow probe were infused with enteral [U-C-13]glut amate (n = 4), enteral [U-C-13]glucose (n = 4), intravenous [U-C-13]glucose (n = 4), or intravenous [U-C-13]glutamine (n = 3). A total of 94% of the e nteral [U-C-13]glutamate but only 6% of the enteral [U-C-13]glucose was uti lized in first pass by the portal-drained viscera (PDV). The PDV extracted 6.5% of the arterial flux of [U-C-13]glucose and 20.4% of the arterial flux of [U-C-13]glutamine. The production of (CO2)-C-13 (percentage of dose) by the PDV from enteral glucose (3%), arterial glucose (27%), enteral glutama te (52%), and arterial glutamine (70%) varied widely The substrates contrib uted 15% (enteral glucose), 19% (arterial glutamine), 29% (arterial glucose ), and 36% (enteral glutamate) of the total production of CO2 by the PDV. E nteral glucose accounted for 18% of the portal alanine and 31% of the porta l lactate carbon outflow. We conclude that, in vivo, three-fourths of the e nergy needs of the PDV are satisfied by the oxidation of glucose, glutamate , and glutamine, and that dietary glutamate is the most important single co ntributor to mucosal oxidative energy generation.