Utilization for protein synthesis in individual rat organs of extracellular 2-ketoisocaproate relative to utilization of extracellular leucine

doi:10.1016/0026-0495(89)90096-6

Metabolism

Volume 38, Issue 7, July 1989, Pages 612-618

https://doi.org/10.1016/0026-0495(89)90096-6 Get rights and content

Abstract

Rats were given constant intravenous infusions of [³H]-leucine plus [1-¹⁴C]-2-ketoisocaproate (KIC). Specific activities of plasma leucine and plasma KIC reached plateaus by two to three hours. ³H specific activity of KIC was 85% ± 2% of that in leucine. ¹⁴C specific activity of leucine was 36% ± 2% of that in KIC. The ¹⁴C/³H ratios in leucine and KIC were constant from the earliest sampling time (one hour) at 0.65 ± 0.03 and 2.20 ± 0.07, respectively. In various tissues, ¹⁴C/³H in free leucine and in tissue protein were approximately equal, but in most organs these ratios were significantly greater than the ratio ¹⁴C/³H in plasma leucine. From these data we estimate that the fraction of leucine incorporated into protein in individual organs derived from extracellular KIC rather than extracellular leucine varies from zero (in liver and bone marrow) to 35% to 45% (in brain and heart), and comprises 12% in the body as a whole.

References (24)

M Walser et al.
Progression of chronic renal failure in patients given ketoacids following amino acids
Kidney Int
(1987)
DG Sapir et al.
Effects of alphaketoisocaproate and of leucine on nitrogen metabolism in postoperative patients
Lancet
(1983)
S Munoz et al.
Utilization of alpha-ketoisocaproate for synthesis of hepatic export proteins and peripheral proteins in normal and cirrhotic subjects
Gastroenterology
(1986)
CW Kang et al.
Effect of the level of dietary protein on the utilization of alpha-ketoisocaproate for protein synthesis
Am J Clin Nutr
(1986)
K Tungsanga et al.
Utilization of alphaketoisocaproate for protein synthesis in chronically uremic rats
Kidney Int
(1986)
DW Matthews et al.
Relationship of plasma leucine and alpha-ketoisocaproate during L-[1-¹³C] leucine infusion in man: A method for measuring human intracellular leucine tracer enrichment
Metabolism
(1982)
M Walser et al.
Measurement of branched-chain ketoacids in plasma by high-performance liquid chromatography
Anal Biochem
(1987)
BA Bidlingmeyer et al.
Rapid analysis of amino acids using pre-column derivatization
J Chromatogr
(1984)
RL Heinrikson et al.
Amino acid analysis by reverse-phase high-erformance liquid chromatography: Precolumn derivatization with phenylisothiocyanate
Anal Biochem
(1984)
KH Winterhalter et al.
Preparation, properties and specific recombination of alpha beta-globin subunits
J Biol Chem
(1964)

DH Baker

Utilization of isomers and analogs of amino acids and other sulfur-containing compounds

Progr Food Nutr Sci

(1986)

HF Herlong et al.

Use of ornithine salts of branched-chain ketoacids in portal-systemic encephalopathy

Ann Intern Med

(1980)

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Gas chromatographic-mass spectrometric determination of α-ketoisocaproic acid and [<sup>2</sup>H<inf>7</inf>]α-ketoisocaproic acid in plasma after derivatization with N-phenyl-1,2-phenylenediamine
2001, Journal of Chromatography B: Biomedical Sciences and Applications
A method for determination of α-ketoisocaproic acid (KIC) and [4,5,5,5,6,6,6-²H₇]α-ketoisocaproic acid ([²H₇]KIC) in rat plasma was developed using gas chromatography–mass spectrometry-selected ion monitoring (GC–MS-SIM). [5,5,5-²H₃]α-Ketoisocaproic acid ([²H₃]KIC) was used as an analytical internal standard to account for losses associated with the extraction, derivatization and chromatography. The keto acids were extracted by cation-exchange chromatography using BondElut SCX cartridge and derivatized with N-phenyl-1,2-phenylenediamine to form N-phenylquinoxalinone derivatives. Quantitation was performed by SIM of the respective molecular ions at m/z 278, 281 and 285 for the derivatives of KIC, [²H₃]KIC and [²H₇]KIC on the electron impact method. The limit of detection was found to be 70 fmol per injection (S/N=3) and the limit of quantitation for [²H₇]KIC was around 50 nM in rat plasma. Endogenous KIC concentrations in 50 μl of rat plasma were measured with relative intra- and inter-day precision of 4.0% and 3.3%, respectively. The intra- and inter-day precision for [²H₇]KIC spiked to rat plasma in the range of 0.1 to 10 μM gave good reproducibility with relative standard deviation (RSD) of 6.5% and 5.4%, respectively. The intra- and inter-day relative errors (RE) for [²H₇]KIC were less than 6.4% and 3.8%, respectively. The method was applied to determine the plasma concentration of [²H₇]KIC after an intravenous administration of [²H₇]KIC in rat.
Role of branched-chain ketoacids in protein metabolism
1990, Kidney International
Ketoanalogues of three branched-chain amino acids (leucine, isoleucine, and valine) are the principal constituents of ketoacid-amino acid mixtures currently under clinical trial in the United States [1], Canada, and France [2] as dietary supplements for patients with chronic renal failure. They have also been studied as agents of possible therapeutic value in portal-systemic encephalopathy [3], congenital hyperammonemia [4], post-operative N wasting [5], muscular dystrophy [6], McArdle's disease [7], and as feed additives for farm animals [8–11].
In addition to their possible uses, these branched-chain ketoacids (BCKA) play a role in normal amino acid metabolism, owing to their rapid interconvertibility (by transamination) with branched-chain amino acids (BCAA). Most of their potential therapeutic uses stem from effects of these compounds on protein turnover.
The purpose of this review is to summarize the current knowledge concerning the role of endogenous BCKA in protein metabolism and the effect of exogenous BCKA on N balance, with particular reference to renal failure. Other aspects of BCKA metabolism have been reviewed recently [12–15].
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2001, European Journal of Biochemistry
Arteriovenous differences and tissue concentrations of branched-chain ketoacids
1993, The Journal of Laboratory and Clinical Medicine
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^☆: Supported by Grant No. DK-32009 from the National Institutes of Health.

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Utilization for protein synthesis in individual rat organs of extracellular 2-ketoisocaproate relative to utilization of extracellular leucine☆

Abstract

Kidney Int

Lancet

Gastroenterology

Am J Clin Nutr