Uric acid transport in brush border membrane vesicles isolated from rabbit kidney.

The transport of uric acid was studied in brush border membrane vesicles isolated from rabbit kidney. The uptake of uric acid by the vesicles was osmotically sensitive and occurred in the absence of significant uric acid degradation. Under the conditions used to evaluate transport, urate binding to the membranes represented only 10--15% of the total uptake. The initial rate of uptake was linear over the concentration range 0.04--8 mM urate. Uptake of urage was Na+ gradient independent. It was dependent on external pH and temperature with Q10 near 3. The urate uptake was inhibited reversibly by p-chloromercuribenzoate. Probenecid, ouabain, cyclic adenosine 3',5'--monophosphate, and its dibutyryl derivative had no appreciable effects. Pyrazinoic acid and pyrazinamide stimulated urate uptake. Experiments performed with osmotically shocked vesicles demonstrated that this stimulatory effect resulted from increased binding of urate to the membranes. These results indicate that in several ways urate transport in vesicles resembles that observed with more physiologically intact preparations.