NERIDRONATE PREFERENTIALLY SUPPRESSES THE URINARY-EXCRETION OF PEPTIDE-BOUND DEOXYPYRIDINOLINE IN POSTMENOPAUSAL WOMEN

ELISAs for measuring the urinary excretion of collagen crosslinks and related peptides appear to show marked differences in sensitivity to a nti-resorptive therapy. This presumably reflects variations in specifi city of the anylate being detected in these assays and the way in whic h they respond to treatment. To clarify these points, we used HPLC ana lysis to assess the effect of four weeks treatment with the amino-bisp hosponate neridronate, on free and peptide-bound fractions of the coll agen cross-links deoxypyridinoline (Dpd) and pyridinoline (Pyd). Six p ostmenopausal women in whom two hour morning urine samples were obtain ed at baseline (x2), and one, two and four weeks after commencing trea tment were included. We found that neridronate had relatively little e ffect on peptide-bound or free urinary Pyd, but markedly reduced pepti de-bound urinary Dpd. However, urinary excretion of free Dpd was not s ignificantly affected. As a consequence of these differential effects on collagen cross-link excretion, neridronate led tn a striking increa se in the free/total Dpd ratio and in the peptide-bound Pyd/Dpd ratio. We conclude that neridronate, and presumably other bisphosphonates, s electively suppresses peptide-bound Dpd excretion possibly reflecting altered processing of collagen crosslinks released during bone resorpt ion.