CIRCADIAN VARIATION OF URINARY TYPE-I COLLAGEN CROSS-LINKED C-TELOPEPTIDE AND FREE AND PEPTIDE-BOUND FORMS OF PYRIDINIUM CROSS-LINKS

This study was performed to investigate the circadian variation of uri nary CrossLaps (CTx), which was the type I collagen peptide released d uring bone matrix degradation, and peptide-bound and free forms of uri nary pyridinium crosslinks, Urine was obtained during the 24 h of the study in seven separate collections as follows: from 23:00 h to the fi rst void (FV) followed by FV at 11:00, 11:00-14:00, 14:00-17: 00, 17:0 0-20:00, 20:00-23:00, and 23:00 h to FV the next morning, Total, free, and peptide-bound pyridinoline (Pyr) and deoxypyridinoline (Dpyr) exc retion measured by highperformance liquid chromatography (HPLC) and CT x measured by enzyme-linked immunosorbent assay in nine premenopausal women aged 22-40 years and nine osteoporotic women aged 65-83 Sears wa s analyzed, Among three parameters of Pyr measured by HPLC, a signific ant day and night difference was found only in total Pyr (21.9% higher at night than during the day in premenopausal women and 24.0% in oste oporotic women, whereas no significant day and night variation was fou nd in free and peptide-bound Pyr in either group, In contrast, total a nd peptide-bound Dpyr were significantly (37.9% and 66.9%) higher at n ight than those during the day in premenopausal women (38.0%) and oste oporotic women (48.8%), For free Dpyr, there were no day and night dif ferences in the two groups, The day and night variances were significa ntly greater in peptide-bound Dpyr than with total Dpyr in both groups , In urinary CTx, a significant circadian variation with a peak at nig ht and a nadir at 17:00 h was found (p < 0.0001) (premenopausal was 54 .0% higher at night than during the day; osteoporotic was 38.4%), In c onclusion, urinary CTx represented remarkable circadian variation comp ared with urinary pyridinium crosslinks measured by HPLC. Furthermore, free pyridinium crosslinks did not undergo a circadian variation, Pep tide-bound crosslinks might contribute mostly to the circadian variati on of total excretion of pyridinium crosslinks. (C) 1998 by Elsevier S cience Inc, All rights reserved.