URINARY-EXCRETION OF ALLANTOIN AND ALLANTOIN PRECURSORS BY SHEEP AFTER DIFFERENT RATES OF PURINE INFUSION INTO THE DUODENUM

Two experiments were carried out to determine endogenous losses and the response of urinary purine derivatives to increased duodenal inputs of purine bases. Four ewes each fitted with a re-entrant cannula at the proximal duodenum, and conventionally fed, were subjected to full replacement of duodenal digesta followed by the administration of a solution either free of purines (Expt 1) or enriched with increasing amounts of purines, to supply 0.48-21.27 mmol/animal per day (Expt 2). Basal daily urinary excretions of allantoin, uric acid, hypoxanthine and xanthine were 11.5 +/- 0.94, 9.9 +/- 0.67, 6.9 +/- 0.46 and 1.2 +/- 0.16 mg/kg W0.75. Allantoin was the only purine derivative which increased in response to incremental inputs of duodenal purines. The relationship between allantoin excretion and infused purines showed a urinary recovery of 0.8 for purines infused at > 220-mu-mol/kg W0.75. Lower rates of infusion did not alter allantoin excretion. The results show urinary allantoin to be a useful index to estimate duodenal input of purines when animals are fed close to or above their energy maintenance requirements.