STANDARDIZATION OF PYRIDINIUM CROSS-LINKS, PYRIDINOLINE AND DEOXYPYRIDINOLINE, FOR USE AS BIOCHEMICAL MARKERS OF COLLAGEN DEGRADATION

The collagen crosslinks, pyridinoline and deoxypyridinoline, have been developed as urinary markers of bone resorption but, despite wide cli nical application of the technique, comparatively little attention has been paid to the standardization of these compounds. In this study, p yridinoline and deoxypyridinoline ha-ve been purified from bone and co nverted completely to monochloride trihydrochloride salts. In addition to mass spectrometry and NMR spectroscopy, the purity of the isolated materials was assessed by microelemental analysis including the chlor ide counterions. These purified compounds were used to establish indiv idual molar absorptivity values as primary standardization criteria fo r the two crosslinks. For pyridinoline in 0.1 mol/L Hcl, epsilon at 29 5 nm was 5490 L mol(-1) cm(-1); in 50 mmol/L sodium phosphate, pH 7.5, epsilon at 325 nm was 5785. The corresponding values for deoxypyridin oline at acid and neutral pH were 5160 and 5290 L mol(-1) cm(-1). The availability of standardization criteria for the crosslinks will allow more meaningful comparisons of clinical data between different labora tories.