Effect of anion exchange inhibitors and para-aminohippurate on the transport of urate in the rat proximal tubule

The present studies were designed to examine the effect of some anion exchange inhibitors and para-aminohippurate (PAH) on urate transport in the proximal tubule of the rat utilizing microperfusion techniques. The addition of SITS, DIDS, or furosemide to the luminal perfusion solution resulted in a decreased rate of absorption of water and 2-¹⁴C-urate. In addition, the presence of PAH in the luminal microperfusion solution resulted in a lower rate of urate absorption. The absorptive flux of urate was significantly higher, however, when PAH was added to the solution microperfusing the capillaries. The capillary to lumen secretory flux of urate was significantly higher when PAH or unlabeled urate was added to the luminal perfusion solution and significantly lower when PAH was added to the capillary perfusion solution. The addition of SITS to either the capillary or luminal microperfusion solution resulted in lower secretory and absorptive fluxes or urate. These studies suggest that both the secretion and reabsorption of urate in the proximal convoluted tubule of the rat is influenced by some anion exchange inhibitors and PAH. The results are considered in conjunction with recent in vitro data suggesting that urate transport is mediated by a process of anion exchange.