Stop-flow analysis of tubular transport of uric acid in rabbits

Abstract

Various physiological and pharmacological aspects of the renal handling of uric acid have been investigated. In the majority of rabbits the free-flow urate-to-inulin clearance ratio was found to be less than 1, although some animals (about 20%) demonstrated net secretion. Despite the predominance of net reabsorption under free-flow conditions, the usual stop-flow pattern showed only a proximal secretory peak. No distal tubular activity was evident under any of the experimental circumstances studied. The administration of chlorothiazide, lactic acid, creatinine, or pyrazinoic acid caused a pronounced increase in the proximal secretory peak. Probenecid produced a depression of the secretory peak resulting in a net reabsorptive dip. This reversal of proximal tubular activity is taken as evidence for the presence of both secretory and reabsorptive mechanisms. The following phenomena have been found to be involved in the renal handling of uric acid by the rabbit: 1) filtration of urate at the glomerulus; 2) proximal reabsorptive and secretory transport systems which are drug sensitive; and 3) relative impermeability of the distal tubule to urate.