FACTORS AFFECTING THE ASSAY OF URINARY 3-HYDROXY PYRIDINIUM CROSS-LINKS OF COLLAGEN AS MARKERS OF BONE-RESORPTION

The measurement of the 3-OH pyridinium compounds, pyridinoline (Pyr) a nd deoxypyridinoline (Dpyr), in urine by high performance liquid chrom atography is potentially useful in clinical studies, since they are sp ecific biochemical markers of bone resorption. The aims of the present study were to improve assay performance and optimize sample collectio n. An isocratic high performance liquid chromatogram (HPLC) separation with baseline resolution was accomplished within 4 min using heptaflu orobutyric acid as an ion-pair. The sample preparation for HPLC, using CF1 cellulose, produced uncontaminated samples with a recovery higher than 90% for both crosslinks. An elastin-derived material, tentativel y identified as isodesmosine (Ides), was also tested and proved to be a suitable internal standard. Use of this standard improved assay prec ision. The effect of an oral gelatin load on the excretion of Pyr and Dyr was investigated. The creatinine corrected excretion of Pyr and Dp yr was unchanged over a 6 h period, in contrast to the 10-fold increas e in the excretion of urinary hydroxyproline with a peak 2-4 h after i ngestion. In 20 postmenopausal women, 2 h fasting morning urine result s correlated with results from 24-h urine collections Dpyr/Cr (r = 0.7 0, n = 20). There was a day-to-day variation of 26% in adults studied for 10 days.