Renal excretion of uric acid in the dog

Abstract

Using clearance and stop-flow techniques, the latter with inulin as the reference solute, a number of physiological variables were examined in the mongrel dog. A few experiments were performed in Dalmatians. In the mongrels, urate clearance was slightly dependent on plasma urate level and the rate of urine flow, but independent of urine pH. Stop-flow studies indicated a proximal site for reabsorption but no evidence for distal secretion (32 experiments). The stop-flow pattern was only slightly modified by high plasma urate levels. Minimal U/Purate [Urine/Plasma] ratios as low as 0.50 were observed. In the mongrel it was difficult to demonstrate significant drug effects on urate excretion. The marked species variations in terms of drug responses remain unexplained. Pyrazinoic acid had no demonstrable action on distal tubular function but lowered urate concentration in stop-flow samples of proximal origin. The results are interpreted in terms of bidirectional active transport of uric acid at a proximal site, a mechanism in basic agreement with that found in other mammalian species.