renal handling of uric acid
Uric acid is a weak organic acid. It is excreted primarily (66%) through the kidney. Up to a third is excreted through the GI tract. In cases of renal failure, GI excretion is increased.
There are four components of renal excretion of uric acid :
- 1. Glomerular filtration: near complete excretion of urate.
- 2. Proximal tubule reabsorption of urate in exchange for organic acids and monocarboxylates (lactate/pyruvate/acetoacetate/hydroxybutyrate): mediated by URAT1 and GLUT9 transporters.
- 3. Tubular secretion of urate more distal in the tubule, mediated by ABCG2 and MRP4 transporters.
- 4. Tubular reabsorption of urate a second time in exchange for dicarboxylates (oxalic acid/malonic acid/succinic acid): mediated by OAT4 and OAT 10 transporter.