DISTAL TUBULAR RESORPTION OF SOME ORGANIC ACIDS IN RAT KIDNEY

Transtubular permeabilities of several organic acids (phenobarbital, sulfamerazine, p-aminohippuric acid, uric acid and N4-acetylsulfamerazine) across the distal convoluted tubule of rat kidney were studied as a function of intratubular pH using microperfusion technique. The resorption of substances like phenobarbital and sulfamerazine increased with their lipid solubility, i.e. with the amount of undissociated molecules. Substances with very low lipid solubility like PAH and uric acid were not reabsorbed when contact times up to 2 sec were used. Although N4-acetylsulfamerazine is soluble in organic solvents to a relatively large extent no resorption across the distal tubule was detected. The permeability of these organic acids across the distal tubular wall is qualitatively similar to that across the proximal convoluted tubules, but differed quantitatively. The permeability constants across the distal tubules of substances with high lipid solubility were only 16-26% of the values found for proximal tubules. © 1969 Springer-Verlag.