THE EFFLUX OF URATE FROM RABBIT RENAL CORTEX SLICES

¹ Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire

The present study was undertaken to evaluate further the in vitro transport characteristics for uric acid. Slices of rabbit kidney cortex were incubated in the presence of high external concentrations of uric acid in order to promote high tissue urate levels. The loaded slices were then transferred at 1-minute intervals through small volumes of urate-free solution, and the efflux of urate was determined. A marked temperature dependence was observed with Q₁₀ values ranging from 2.3 to 3.0. Sodium acetate (10^-2 M) failed to have any effect on urate efflux whereas sodium succinate (10^-2 M) significantly increased it. Potassium-free solutions markedly increased the runout rate, but calcium-free solutions had no effect.

2,4-Dinitrophenol produced a biphasic effect over a 100-fold concentration range. At low concentrations dinitrophenol increased the efflux while at high concentrations the rate of runout was reduced below control levels. No effect of probenecid was noted over the concentration range of 10^-6 to 3 x 10^-4 M. The same was true for p-aminohippurate (PAH) over a similar concentration range.

When these data are compared with those for PAH efflux under similar experimental conditions, relatively few similarities are noted. It appears, therefore, that urate is not extruded from preloaded renal slices by the same process by which PAH is handled.