RENAL AND SALIVARY CLEARANCE OF PURINE DERIVATIVES IN SHEEP

Four adult ewes (mean weight 42.6 kg) fitted with oesophageal fistulae were given 5 mmol/day of allantoin or saline solutions by intrajugula r continuous infusion. The experiment was a randomized cross-over desi gn, with two consecutive 3-day infusion periods. One kg/day fresh matt er of either chopped or pelleted fescue hay was distributed over 12 me als and salivary flow estimated from dilution of Co-EDTA infused into the buccal cavity. Allantoin infusion resulted in a rapid increase in its plasma concentration (84 to 128 (s.e. 1.5) mu mol/l) and urinary e xcretion (9.6 to 13.3 (s.e. 0.18) mmol/day) without significant differ ences between diets. Salivary allantoin also increased (4.6 to 6.4 (s. e. 0.60) mu mol/l) in response to infusion, although the concentration of total purine derivatives in saliva was only proportionately 0.08 t hat of plasma. Renal and salivary clearance of oxypurines, allantoin ( 78 (s.e. 5.0) ml/min and 13 (s.e. 0.7) ml/h), uric acid (466 (s.e. 98. 0) ml/min and 45 (s.e. 9.8) ml/h) and creatinine (104 (s.e. 3.0) ml/mi n and 14 (s.e. 1.1) ml/h) were constant, irrespective of diet and infu sion treatments. Urinary recovery of infused allantoin averaged 0.78 ( s.e. 0.031) but salivary secretion, equivalent to about 0.003 of urina ry losses, was not the explanation for the incomplete recovery.