Determination of leucine metabolism and protein turnover in sheep, using gas–liquid chromatography–mass spectrometry

• Published in: British journal of nutrition 1988-01, Vol.59 (1), p.155-164
• Main Authors: Krishnamurti, C. R., Janssens, S. M.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Female; Fundamental and applied biological sciences. Psychology; Gas Chromatography-Mass Spectrometry; General Nutrition papers; Leucine - blood; Metabolisms and neurohumoral controls; Nitrogen metabolism. Proteins. Glycoproteins. Nucleic acids. Collagen; Protein Biosynthesis; Proteins - metabolism; Sheep - metabolism; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0007-1145; 1475-2662
• DOI: 10.1079/BJN19880019

1. Whole-body protein synthetic rates in non-pregnant ewes were determined by the continuous infusion of L-[15N]- and [1-13C]leucine and measuring the plasma enrichment of leucine, α-ketoisocaproate (α-KIC) and expired carbon dioxide by gas–liquid chromatography–mass spectrometry. 2. The mean whole-body protein synthesis estimated from plasma leucine flux corrected for oxidation was 5·38 (SE 0·54) g/kg per d. 3. Under the conditions of the present study leucine oxidation was 0·323 (SE 0·067) mmol/kg per d and accounted for 10·71 (SE 2·26) % of plasma [13C]leucine flux. Deamination of leucine was 0·55 (SE 0·035) mmol/kg per d and accounted for approximately 17% of plasma [15N]leucine flux. 4. The rate of α-KIC reamination to leucine, calculated by subtracting 13C flux from 15N flux, was 0·228 (SE 0·101) mmol/kg per d. 5. The rate of whole-body protein degradation was 4·49 (SE 0·54) g/kg per d and there was a net protein gain of 0·89 (SE 0·21) g/kg per d.