Time after Feeding and Dietary Arginine Deficiency Alter Splanchnic and Hepatic Amino Acid Flux in Rats

Abstract

The effect of an arginine-deficient diet containing 3.4% glutamate on net flux of amino acids across the portal-drained viscera and liver was studied in rats at 0, 1 or 2 h after a meal and compared with that in arginine-fed controls. Net portal-drained viscera flux for most amino acids was greater in the fed state compared with the postabsorptive state except for glycine and cystine, which did not change, and methionine, which declined. Net amino acid recovery in portal blood 2 h after feeding compared with amounts consumed was highest for alanine (17.3%); recovery of other amino acids ranged from 5.6 to 15.3%. No net portal-drained viscera recovery of consumed cystine was observed. For the branched-chain and aromatic amino acids, methionine, threonine, histidine and lysine, net hepatic uptake was nearly equal to net portal-drained viscera absorption (range 77-127% of portal-drained viscera flux). Correlation coefficients between net hepatic and portal-drained viscera fluxes for leucine, valine, isoleucine, methionine and phenylalanine were 0.84 to 0.93. Postabsorptive hepatic extraction for most amino acids was zero, but after a meal, ranged from 13.3 to 22.9% for the branched-chain and aromatic amino acids. Net hepatic production of ornithine and proline occurred in arginine-fed control rats. This value was near zero for ornithine in rats fed the arginine-deficient diet. Models of interorgan amino acid metabolism in the food-deprived and fed state are presented.