Kinetic studies on transport of PAH and other organic acids in isolated renal tubules

Abstract

Studies were made on the uptake and washout of PAH and other organic acids in isolated renal tubules and cells at 25 C. The renal tubules accumulated PAH rapidly in the first 30-min period. Probenecid, its diethyl- and dimethyl analogues, hippuric acid, and 2,4-dinitrophenol inhibited the tubular transport of PAH competitively. A relationship between the inhibitory effect and the partition coefficient of the compound was observed; the higher the partition coefficient, the greater the inhibition. DNP was also accumulated in the isolated renal tubules. This accumulation was depressed by probenecid, indicating that DNP is probably transported by the same tubular transport mechanism for PAH and other organic acids. In washout experiments probenecid and DNP showed a biphasic action, namely, they stimulated the PAH washout in low concentration and inhibited it in high concentration However, hippuric acid, which has a low partition coefficient, demonstrated an augmentation of PAH washout even at a concentration of 2 x 10^–2 m