MECHANISMS OF HYPERURICEMIA IN CYCLOSPORINE-TREATED RENAL TRANSPLANTED CHILDREN

Mechanisms of hyperuricemia were investigated in 19 pediatric renal tr ansplant recipients 6 months after transplantation. Cr-51-EDTA, PAH, l ithium and sodium clearances. 24-hour urinary creatinine and urate exc retions were measured. Ten patients had hyperuricemia. The hyperuricem ic patients had lower EDTA, PAH, and urate clearances (mean 69.5 vs. 9 2.5, p < 0.05, 234 vs. 421, p < 0.05 and 4.3 vs. 10.6 ml/min/1.73 m(2) , p < 0.001, respectively). Serum urate concentration correlated with cyclosporine dose (r = 0.46, p < 0.05) and inversely with urate (r = - 0.88, p < 0.001), and lithium (r = -0.55, p < 0.05) clearances. Urate clearance showed a significant positive correlation with lithium clear ance (r = 0.66, p = 0.01) and an inverse correlation with fractional p roximal tubular reabsorption (r = -0.63, p = 0.02). Results were not i nfluenced by diuretic administration. Our data support increased proxi mal tubular urate reabsorption rather than decreased secretion as the mechanism in cyclosporine-induced hyperuricemia.