Effects of pyrazinoate and p-aminohippurate on renal urate excretion by the dog and guinea pig.

In anesthetized dogs, pyrazinoate reduced the fractional excretion of urate when the concentration of the drug in plasma ranged from 3 to 300 micrograms/ml. At higher concentrations, fractional excretion rose progressively. p-Aminohippurate at concentrations in plasma ranging from 1 to 1000 micrograms/ml had no effect on the fractional excretion of urate. In guinea pigs, pyrazinoate exerted only a faint uricosuric action and p-aminohippurate was without effect. Both substances were tested over the range of 1 to 1000 micrograms/ml of plasma. The results in dogs help explain some previous reports of negative experiments with pyrazinoate; the doses used were not optimal for detecting responses. The results in guinea pigs suggested that urate secretion in this animal does not fit either of two previously recognized mechanisms.