The defect of uric acid metabolism in Eck-fistula rats.

Because of the discovery of uric acid urolithiasis in rats after end-to-side portacaval anastomosis (PCA), uric acid metabolism was studied in these animals and in appropriate controls. Hyperuricemia and hyperuricosuria were observed in all experimental rats. The fraction of purine catabolites excreted in the urine as uric acid increased from an average of 4.8% to 15.3%. If 14C-uric specifically labeled at position 6 (6-14C-ua) was infused intravenously and the exhalation of 14CO2 was used to calculate a hepatic uric acid clearance, it decreased from 2.14 to 0.97 ml/min/100 gm despite a normal content of hepatic uricase activity as measured in liver homogenates. The fraction of the filtered amount of uric acid excreted in the urine increased from an average of 11% to 30%. Increased supersaturation of the urine with uric acid after PCA may be expected to contribute to the formation of uric acid urolithiasis. This investigation defines a hepatic and renal functional defect in uric acid metabolism which occurs as a result of the PCA.