Ketoisocaproate contamination errors in protein synthesis determinations using L[1-14C]leucine.
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.
López Hellin
J
J
Unitat de Recerques Metabòliques S. Grisolía, Hospital Vall d'Hebron, Barcelona, Spain.
Schwartz
S
S
Garlick
P J
PJ
Rosell
M
M
Arbós
M A
MA
Andreu
A L
AL
García
E
E
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
D002250:Carbon Radioisotopes; D007651:Keto Acids; C013082:alpha-ketoisocaproic acid; D007930:Leucine