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Time after Feeding and Dietary Arginine Deficiency Alter Splanchnic and Hepatic Amino Acid Flux in Rats^1,2,

U.S. Department of Agriculture, Agricultural Research Service, Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111

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.

KEY WORDS: • rats • arginine • hepatic flux • branched-chain amino acids • tyrosine

¹ Mention of a trade name, proprietary product or specific equipment does not constitute a guarantee by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

Manuscript received 28 October 1992. Revision accepted 20 May 1993.