Urinary Excretion of Purines in Sheep with Experimental Orotic Aciduria

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Abstract
Urinary excretion of uric acid, hypoxanthine, allantoin, and urea was measured in sheep (Polish Merino, about 20 kg b.w.) with experimental orotic aciduria. The 240 min infusion of 6-azauridine solution into the jugular vein induced a highly significant increase of urinary orotic acid, uric acid and hypoxanthine excretion. No differences were found in relation to excretion of allantoin and urea in examined sheep. It was calculated that renal clearance of uric acid and hypoxanthine increased significantly in response to 6-azauridine infusion. Intravenous infusion of sodium orotate evoked a highly significant elevation of renal urate clearance. No significant change in renal urea clearance was observed. The data suggest that competition between the renal transport of orotate and actively transported purine compounds (uric acid and hypoxanthine) occurs.