DIETARY ARGININE DEFICIENCY AND GUT AMMONIUM INFUSION ALTER FLUX OF UREA CYCLE INTERMEDIATES ACROSS THE PORTAL-DRAINED VISCERA OF PIGS

The objective of these experiments in pigs were to test the hypotheses that 1) gut synthetic processes could adapt to additional dietary glu tamate or ornithine to meet tissue needs for arginine with feeding arg inine-deficient diets and 2) acute elevation of ammonium in the hepati c-portal blood leads to increased glutamine production. Arterial [117 +/- 5.3 (arginine-deficient) vs. 78 +/- 5 (arginine-adequate) mu mol/L ] and portal ammonium concentrations were elevated in pigs fed arginin e-deficient diets. Dietary ornithine, which elevated portal-drained vi sceral flux of ornithine, corrected the urinary erotic aciduria, but n ot the hyperammonemia seen with feeding arginine-deficient diets. Conc entrations or portal drained viscera fluxes of arginine, ornithine, gl utamate and glutamine were not altered even though portal and arterial ammonium concentrations were increased 8- and 3.5-fold with mesenteri c infusion of ammonium. It was concluded that 1) substitution of gluta mate for glycine or alanine does not alter gut production of ornithine , citrulline or arginine; 2) gut citrulline production is not altered by levels of dietary arginine, ornithine or glutamate; 3) increased am monium challenge does not lead to increased glutamine production even though peripheral ammonium levels increased over threefold; and 4) pro vision of arginine for tissue needs will have to be met from dietary s ources, as adaptations in gut synthetic processes seem to be refractor y to dietary arginine status.