Interorganal relationships of amino acid metabolism in fed rats
Yamamoto, H.; Aikawa, T.; Matsutaka, H.; Okuda, T.; Ishikawa, E.
American Journal of Physiology 226(6): 1428-1433
1974
ISSN/ISBN: 0002-9513 PMID: 4833999 Document Number: 74585
Male Sprague-Dawley rats of 135 to 140 g reared on a commercial diet were starved for 24 h or meal-fed for 2 h each day with a diet based on 30% casein for 7 to 8 days. Blood was removed under anaesthesia from the abdominal aorta of 4 fasted rats, and from the aorta, inferior vena cava and portal, hepatic and renal veins of different groups of 4 meal-fed rats, at 2 h and 4 h after eating. This was repeated 3 times. Plasma amino acid concentrations and the amino acid content of casein were estimated microbiologically, enzymically and by automatic liquid-phase chromatography. Except for glycine, which was higher, and glutamine and arginine, which were similar, amino acid concentrations in the aorta were lower in fasted than in fed rats. Differences in amino acid concentrations in the portal vein and artery of fed rats were generally consistent with the amino acid content of casein, save for glutamine, glutamate and aspartate, which were lower. Amino acid concentrations in the artery, hepatic vein and vena cava were similar, except that glutamine, glycine and the branched-chain amino acids were higher in the hepatic vein than in the aorta, and that proline, alanine and the branched-chain amino acids were higher in the aorta and hepatic vein than in the vena cava. Arterial plasma had a higher content of glutamine, proline, alanine, lysine and branched-chain amino acids than renal vein plasma, but was lower in serine, and in alanine and threonine 4 h after feeding. The differences indicated that most amino acids absorbed into the portal vein were taken up by the liver, although branched-chain amino acids were used by peripheral tissues and the kidney; and that metabolised amino acid N was restored to the circulation as glutamine, alanine, glycine and serine in different proportions by the organs studied.