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      Evaluation of urinary hydroxypyridinium crosslink measurements as resorption markers in metabolic bone diseases.

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          Abstract

          Analyses of the urinary concentration relative to creatinine of the collagen crosslinks, pyridinoline (Pyd) and deoxy-pyridinoline (Dpd) were made in 47 patients with metabolic bone diseases to assess the validity of these assays as indicators of bone resorption. The mean values for patients with Paget's disease of bone, primary hyperparathyroidism and osteomalacia were significantly higher (P less than 0.001) than those for age-matched healthy individuals. During treatment of Paget's disease with bisphosphonates, there was a steady decline in the urinary concentration of the crosslinks to the normal range; this change occurred earlier than for serum alkaline phosphatase. There were significant correlations (P less than 0.01) between the concentrations of both crosslinks and the corresponding values for hydroxyproline. At lower crosslink concentrations, however, these relationships were less marked due to large variations in hydroxyproline values. The results show that measurements of urinary Pyd and Dpd provide clinically applicable indices of bone resorption that are more specific than other markers.

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          Most cited references 19

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          Quantitation of hydroxypyridinium crosslinks in collagen by high-performance liquid chromatography.

          An HPLC method for quantifying the 3-hydroxypyridinium crosslinks of collagen is described. It can be applied to crude hydrolysates of all types of connective tissue. Mineralized tissues can be hydrolyzed directly and analyzed without interference from the mineral ions. The hydroxylysyl (HP) and lysyl (LP) forms of hydroxypyridinium residue were resolved on a reverse-phase C18 column using a gradient of acetonitrile in water and 0.01 M n-heptafluorobutyric acid as an ion-pairing agent. The crosslinking amino acids were accurately quantified down to 2 PM (1 ng) injected, by detecting their natural fluorescence with a spectrofluorometer. Tissues in which hydroxypyridinium crosslinks were plentiful included all forms of cartilage, bone, dentin, ligament, tendon, fascia, intervertebral disc, lung, gut, cervix, aorta, and vitreous humor. Among normal tissues, LP, the minor form of the crosslink, was present in significant amounts relative to HP only in bone and dentin. Both crosslinks were essentially absent from skin, cornea, rat tail tendon, and basement membranes.
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            Collagen cross-linking in human bone and articular cartilage. Age-related changes in the content of mature hydroxypyridinium residues.

            The concentration in collagen of hydroxypyridinium cross-linking amino acids was measured in samples of bone and cartilage from human subjects aged from 1 month to 80 years. Cortical and cancellous bone samples were dissected and analysed separately. In both bone and cartilage, the content of this mature form of cross-link reached a maximum by 10-15 years of age (the amount in cartilage being 5-10 times that in bone), then stayed essentially in the same range throughout adult life. In bone the ratio of the two chemical variants of the mature cross-link, hydroxylysylpyridinoline to lysylpyridinoline, was constant throughout adult life at 3.5:1, whereas in cartilage it was always greater than 10:1. The ratio of hydroxypyridinium cross-links to borohydride-reducible keto-amine cross-links also changed with age. The reducible cross-links in bone collagen decreased steeply in content between birth and 25 years, but persisted in significant amounts throughout adult life. Reducible cross-links had virtually disappeared from cartilage by 10-15 years of age, being replaced by hydroxypyridinium residues, their maturation products. Cancellous and cortical bone collagens showed similar trends with age in their content of mature cross-links, though for each subject the concentration in cancellous bone was always lower than in cortical bone, presumably reflecting the higher turnover rate and hence the more immature state of cancellous bone.
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              Quantitative analysis of the pyridinium crosslinks of collagen in urine using ion-paired reversed-phase high-performance liquid chromatography.

              A method has been developed for the simultaneous and rapid analysis of the 3-hydroxypyridinium crosslinks of mature collagen, pyridinoline and deoxypyridinoline, in samples of urine and tissue. After hydrolysis in 6 M HCl, samples were prefractionated by partition chromatography using columns packed with cellulose CF1. The appropriate fractions were freeze-dried and then subjected to high-performance liquid chromatography using a gradient system with 20 mM NH4Cl, pH 3.5, and acetonitrile, incorporating 1-octanesulfonic acid as an ion-pairing agent; the pyridinium crosslinks were detected fluorometrically. The limit of detection of both crosslinks was 1 pmol. The mean recoveries of added standard to samples ranged between 94.2 and 97.2%, and the reproducibility of the complete procedure was between 12 and 16%. An application of the method in the study of degenerative disorders of bone and connective tissue is illustrated.
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                Author and article information

                Journal
                Eur. J. Clin. Invest.
                European journal of clinical investigation
                Wiley
                0014-2972
                0014-2972
                Jun 1991
                : 21
                : 3
                Affiliations
                [1 ] Biochemical Sciences Division, Rowett Research Institute, Bucksburn, Aberdeen, Scotland.
                Article
                10.1111/j.1365-2362.1991.tb01375.x
                1909635

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