MONITORING OF BONE-RESORPTION AFTER RENAL-TRANSPLANTATION BY MEASURING THE URINARY-EXCRETION OF PYRIDINIUM CROSS-LINKS

The urinary excretion of pyridinium cross-links was measured in 70 sec ond morning urine samples from 49 patients following renal transplanta tion. One and three months after renal transplantation, the urinary ex cretion of pyridinium cross-links was higher (p < 0.05) than at one we ek after transplantation. At all times after transplantation, the valu es for the excretion of pyridinium cross-links were correlated with th e bone alkaline phosphatase concentrations (p < 0.001). However, there was no correlation between parathyrin concentrations and the values f or the excretion of pyridinium cross-links (p > 0.05). This rise in th e excretion of pyridinium cross-links is probably due to an increase o f bone resorption caused by cyclosporin A and/or glucocorticoids. In t he case of 17 urines with excretion values of pyridinium cross-links a bove the upper reference limit (pyridinoline equivalents, 93 mu mol/mo l creatinine), only 2 (12%) of the corresponding sera showed increased bone alkaline phosphatase values. In patients following renal transpl antation simultaneous assessment of bone formation and bone resorption (determined from bone alkaline phosphatase serum concentrations and t he excretion of pyridinium cross-links) may therefore enhance the diag nostic sensitivity for detecting effects on bone metabolism.