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Radioisotope Service, Department of Medicine, Veterans Administration Hospital; Department of Medicine, New York University School of Medicine; and Department of Biochemistry, New York University College of Dentistry
The effects of amino acids on albumin synthesis were measured in 47 studies using the isolated perfused rabbit liver. Carbon-14 carbonate was used to label the hepatic intracellular arginine pool, and hence, the carbon of urea and the guanido carbon of arginine. Amino acid levels in the perfusate and in the liver were determined. All studies were run for 2.5 hours to assure release of labeled albumin. Livers obtained from fasted rabbits synthesized 18 ± 1.1 mg of albumin 117 ± 8 mg of urea. The addition of methionine, lysine, leucine, valine, or threonine, at 10 µmoles/ml, failed to alter albumin synthesis. Tryptophan at 0.05 to 10.0 µmoles/ml increased albumin synthesis 138 to 175%, and urea synthesis by 56%. The addition of isoleucine also resulted in an 89% increase in albumin synthesis, and both isoleucine and tryptophan resulted in ribosomal reaggregation. When the donor rabbits were fed, albumin synthesis averaged 33 mg, and no increase was observed with tryptophan or isoleucine. Results of these studies are compatible with the concept that tryptophan stimulates the ribosomal reaggregation with enhanced albumin production. Isoleucine, while effecting reaggregation, may be either less efficient in this regard or less specific for albumin.
2 Presented in part at the American Association for the Study of Liver Disease, Chicago, Illinois, 1968.
Manuscript received 28 February 1969.
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