Assay for 5-hydroxylysine and L-lysine in human and rat urine and in bone by gas chromatography

An accurate method for the determination of collagen to study its distribution and turn-over in different tissues is described. 5-Hydroxylysine (5Hylys) is an amino acid that is apparently present in no other protein except collagen and, as it is metabolised only to a minor degree compared with 4-hydroxyproline (4Hypro), it has been suggested as a better marker of the collagen metabolism. Interest in this amino acid has increased recently because the levels of 5Hylys in urine and in different tissues may offer a new basis for detecting pathologies of the collagen molecule. This paper describes a method for the quantitative determination of 5Hylys and lysine (Lys) by gas chromatography (GC) in human and rat urine and in rat bone. The limit of detection was 350 pmol ml-1 for 5Hylys and 200 pmol ml-1 for Lys for all the biological samples. This method therefore provides a complete view of the metabolism of this amino acid and of the tissue it comes from.