Effect of chronic experimental renal insufficiency on urate metabolism.

The rise in plasma uric acid (UA) in chronic renal failure (CRF) is quite limited. This may be due to either increased extrarenal excretion, diminished biosynthesis, and/or enhanced degradation of uric acid. The intestinal flux studies revealed a striking modification of urate transport from no net flux to a net secretory flux in the jejunum and from a basal net absorptive to a net secretory flux in the colon of CRF animals. In addition, CRF animals showed a marked reduction in hepatic, renal, and enteric tissue xanthine oxidase activity and no significant change in tissue uricase activity. The correction of anemia with erythropoietin did not significantly alter the plasma concentration or urinary excretion of urate. Thus, enhanced enteric excretion and depressed production of uric acid (reduced xanthine oxidase activity) may account for the lack of significant hyperuricemia in CRF.