Renal excretory transport of organic acids: inhibition by oxypurines

Uric acid inhibited the active accumulation of p-aminohippurate (PAH) by surviving slices of rabbit kidney cortex without affecting oxygen utilization or oxidative phosphorylation. The inhibitory potency of uric acid was compared with that of several desoxyurates and N-methylated urates. In general, the desoxyurates were less potent and the N-methylated urates more potent inhibitors than uric acid. The data suggest that the inhibitory reaction requires the presence of all three oxygen atoms of the urate molecule. These appear to function as carbonyl groups rather than as enolic hydroxyl groups in a predominantly nonionic reaction.