title: Ketoisocaproate contamination errors in protein synthesis determinations using L[1-14C]leucine.
abstract: Protein synthesis rate determinations in vivo using L-[1-14C]-leucine may be underestimated because of contamination by radioactive ketoisocaproate (KIC) resulting from leucine metabolism. The aim of this work was to set up a reliable method to determine the KIC/leucine radioactivity ratio in protein-free homogenates, and to apply it to study the extent of the protein synthesis ratio error due to KIC contamination. Cation-exchange chromatography using Dowex AG 50W-X8 resin was used to separate KIC from leucine, eluting KIC with water and leucine with 4 M ammonia. The errors found in the protein synthesis ratio were 6.20% in liver and 2.34% in jejunum.
authors.affiliation: Unitat de Recerques Metabòliques S. Grisolía, Hospital Vall d'Hebron, Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: López Hellin
authors.forename: S
authors.initials: S
authors.lastname: Schwartz
authors.forename: P J
authors.initials: PJ
authors.lastname: Garlick
authors.forename: M
authors.initials: M
authors.lastname: Rosell
authors.forename: M A
authors.initials: MA
authors.lastname: Arbós
authors.forename: A L
authors.initials: AL
authors.lastname: Andreu
authors.forename: E
authors.initials: E
authors.lastname: García
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D002852:Chromatography, Ion Exchange; D004340:Drug Contamination; D007413:Intestinal Mucosa / Q000378:metabolism*; D007583:Jejunum; D007651:Keto Acids / Q000302:isolation & purification / Q000378:metabolism; D007930:Leucine / Q000302:isolation & purification / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D014176:Protein Biosynthesis; D011865:Radioisotope Dilution Technique; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002250:Carbon Radioisotopes; D007651:Keto Acids; C013082:alpha-ketoisocaproic acid; D007930:Leucine